How do i get to the countdown timer on my sport line solo 900

There is single manual for all adidas watches. You can find procedure for your watch.

ADIDAS-ORIGINALS-TIMEPIECES_CARE-MANUALS_EN.pdf (adidaswatches.com)

just bring it to the authorized retailer of your watch because they really know ho to change your watch battery

MODE (LONG PRESS-4 SEC) TO ENTER INTO SETTINGS;

UP/DOWN TO CHANGE THE PARAMETERS; \

*C/*F KEY TO TOGGLE BETWEEN TO TEMPERATURE FORMAT;

SNOOZE BUTTON TO SET SNOOZE IN ALARM-MULTIPLE SNOOZE CAN BE SET;

RESET KEY CAN BE USED TO RESET CLOCK TO DEFAULT;

DAY COUNTDOWN , AND TIME COUNTDOWN CAN BE ADJUSTED;

DETAILED INFORMATION TO SET THE CLOCK

INSERT CELLS;-SCREEN SHOWS DEFAULT VALUES-INITIAL MUSIC WILL RING;
LONG PRESS MODE BUTTON-KEEP IT PRESSED UNTIL 12 STARTS BLINKING;
USE UP /DOWN BUTTON TO ADJUST HOURS...
THEN SIMPLY PRESS MODE AGAIN, NOW MINUTES 00 IS DEFAULT WILL START BLINKING;
USE UP/DOWN BUTTON TO ADJUST MINUTES;
AGAIN PRESS MODE, SCREEN WILL SHOW YEAR 2002 DEFAULT BLINKING, USE UP/DOWN KEY TO ADJUST YEAR;
AGAIN PRESS MODE, SCREEN WILL SHOW MONTH BLINKING, USE UP/DOWN KEY TO ADJUST CURRENT MONTH;
AGAIN PRESS MODE, SCREEN WILL SHOW DATE BLINKING, USE UP/DOWN KEY TO ADJUST YEAR;
AGAIN PRESS MODE, SCREEN WILL SHOW 12:00 BLINKING WITH ALARM SIGN (FOR ALARM SET);USE UP/DOWN KEYS TO SET ALARM, FIRST HOURS AND THEN MINUTES FOR ALARM; THEN ON PRESSING YOU CAN SELECT SNOOZE MINUTES;
AFTER SNOOZE ON PRESSING MODE AGAIN YOU CAN SELECT DAY COUNTDOWN TO SELECT 999 DAYS COUNTDOWN FROM CURRENT DATE;

when watch displays time and everything .....
each and every buttons has some function;(shortcuts)
press down to toggle between 12hr/24hr format;
press up to enter contdown timer;
press snooze to set snooze in alarm;
press c/f to toggle between two temperature formats;
press mode to toggle between alarm time and current time;

The crown has 3 positions.

Normal screwed down.
First pull out position.
Second pull out position.

Setting the Time:
Pull out the crown to position 3.
Rotate the crown to set the exact time.
Ensure that you are in the daytime12 hour segment by allowing the hands to pass 12 o'clock and notice if the date moved on or not.
If the date changed, then you will need to advance at least 2 hours before moving on to set the date.
If you do not need to change the date, return the crown to position 1.


Setting the Date:
DO NOT DO THIS IF THE WATCH IS BETWEEN 8pm & 2am
Pull crown to position 2.
Rotate the crown clockwise to set to the correct date.
Return the crown to position 1.


Setting the Alarm [12 hour]
Pull the crown to position 2.
Rotate the crown anti clockwise to move the alarm hand to the desired time.
Return the crown to position 1.
To activate the alarm, press the 8 o'clock button. You will hear 2 beeps.
To deactivate the alarm, press the 8 o'clock button. You will hear 1 beep.
NB If the alarm is not cancelled while it sounds the first time, it will repeat again in 2 minutes time. The alarm sound last for 15 seconds. If the alarm time coincides with 1 beep of the countdown, the alarm function will be cancelled.


Battery EOL [End Of Life]
The Swiss ISA 8270 movement uses a 395 cell and will signify a low power state by advancing the small seconds hand 4 steps every 4 seconds.


Setting the Countdown
You can specify a countdown of between 1 and 10 minutes.
Press the 4 o'clock button to enter setting mode. You will hear 1 beep.
Press the 4 o'clock button to move the central timing hand successively to the desired countdown time.
Wait 3 seconds for the watch to automatically exit the setting mode.
You can change the duration of the countdown [except in the last minute] at any time.
e.g. If the countdown is set to 10minutes, and you now want to change the countdown to 9 minutes, press the 4 o'clock button. The hours/seconds counter sub-dial will perform one complete turn and then stop at 60, before continuing.


Activating the Countdown:
Press the 2 o'clock button to start the countdown. You will hear 2 beeps.
The hours/seconds counter sub-dial will perform one complete turn and then stop at 60, before continuing.
When the countdown begins, the hour/seconds counter sub-dial indicates the seconds with 1 step every 2 seconds, and the central timing hand indicates the minutes with 1 step being 2.4 seconds.


Countdown tone:
There are 2 beeps every minute.
in the last minute:
50 seconds=1 beep.
40 seconds=1 beep.
30 seconds=2 beeps.
20 seconds=2 beeps.
10 seconds and less=1 beep every second with zero being 1 second long beep. Timer function automatically starts.


Timer:
After countdown has finished the timer starts automatically.
The central timing hand indicates the minutes with 1 step every 12 seconds. The hour/minutes counter sub-dial indicates the hours up to a maximum of 96.
Press the 4 o'clock button to see the timer seconds [display lasts up to a minute].
Press the 4 o'clock button to see the timer hours.
The timer has a maximum time of 96 hours [4 days] after which the hour/seconds sub-dial counter will stay at 0 and the central timing hand will stay at 12.


Start/Stop Timer:
Press the 2 o'clock button to stop the timer. You will hear 1 beep.
Press the 2 o'clock button to resume the timer. You will hear 2 beeps.


Setting the Countdown & Timer:
Countdown reset:
Press the 2 o'clock button to stop the countdown. You will hear 1 beep.
Press the 4 o'clock button to reset.


Setting the Timer:
Press the 2 o'clock button to stop the timer. The hour/seconds counter sub-dial will show the elapsed hours and the central timing hand the elapsed minutes.
Press the 4 o'clock button to view the seconds elapsed on the hour/seconds counter sub-dial.
Press the 4 o'clock button to reset.


Resetting the Hands:
If the hands do not zero correctly, which might occur after a battery change or a violent shock, you can make adjustments by doing the following settings as long as the countdown is not in operation.
To correct the hour/seconds counter sub-dial, pull the crown out to position 2 and wait 1 second.
Press either the 2 or 4 o'clock button; the central timing hand will turn and stop [not necessarily at 12].
Press the 2 o'clock button to increment the hours/seconds counter sub-dial hand to position it at 60.
To correct the central timing hand, press the 4 o'clock button to increment the hand to the 12 position.
Return the crown to position 1.



If the battery had been replaced, the central timing hand defaults to the 10 minute position. If the battery had not been replaced, the central timing hand will return to the previously set position.

Thank you for contacting FixYa.

Setting the Time and Date
1. To set the time and date on your Armitron digital watch, begin by pressing the "A" button while in time-telling mode. The seconds place will begin to flash; press the "C" button to reset the seconds to "00". Press "B" to set the hour, and press the "C" button repeatedly until the desired hour is reached. Press "B" to set the minutes, pressing the "C" button until the desired minute is reached. Press the "B" button, followed by "C" to set the month, date and day of the week. When you are finished programming the time and date, press "A" to save and return to time-telling mode.
Using the Chronograph
2. To use the chronograph feature on your digital Armitron watch, press "B" while in time-telling mode to access chronograph mode. Press the "C" button to start the timing; press "C" a second time to stop the timing. To reset the chronograph, press the "A" button. Press the "B" button at any time to return to time-telling mode.
Using the Split Lap Chronograph Feature
3. To use the split lap feature on an Armitron digital watch, press the "C" button while in chronograph mode. Press the "A" button to measure splits or laps; at the end of the event, press the "C" button to stop the timing. Press "A" once to see the final split or lap time, press "A" twice to reset the chronograph to "0". Return to time-telling mode by pressing the "B" button.
Setting an Alarm
4. To set an alarm on your Armitron digital watch, press the "B" button twice to access the alarm mode. Press the "A" button and wait for the hours place to begin flashing, then press the "B" button twice. Press the "B" button, followed by the "C" button to set the hour and minute of your alarm. When you're finished, press the "A" button to save the alarm. Press the "B" button to return to time-telling mode.
Using the Countdown Timer
5. To use your Armitron digital watch as a stopwatch, begin by pressing the "B" button three times while in time-telling mode to access the countdown timer mode. Press the "A" button, followed by the "C" button to set the hour. Press the "B" button, followed by the "C" button to set the minutes and seconds. Once you've set your timer, press "A" to return to countdown timer mode. To stop the countdown timer, press the "C" button. When you are ready to reset the countdown timer, press the "A" button. To return to time-telling mode, press the "B" button.

Best regards. Jewel

Please make sure you are in time mode. Now hold your bottom right button in for 2-3 seconds. You will see a heart pop up over the seconds. Now you will be able to take your heart rate.

remove battery - replace battery and short AC Pad and battery to reset

If you have no markings on bezel there is no practical use for this feature.
Bezels with markings are used as a tachymeter (for calculating speed of the moving object) or as a countdown timer for sporting events or diving.
In your case bezel is becoming loose and thats why it is turning as I can't see the point why the watch should be fitted with rotating bezel with no markings on it.

Rate me, please.