How to remove watch back

Question edited for clarity.

I really need the model number, then I can find you a manual. There are press button instructions in the link.

https://www.google.com/search?q=Sekonda+5atm+watch+digital%2C+adjust+hands

Sekonda Watch Instruction Manuals

https://www.sekonda.com > instruction-manuals
Find the correct instruction manual for your Sekonda watch model. ... Instruction manuals. You can find your model number on the back of your watch.

..

Question edited for clarity.
Question moved to Watches from Sewing Machines.

Here is every Sekonda Manual. Look for a 4 number code on the back. Normally there is a button combination that moves the hands fast or a click at a time like an alarm clock or timer.

https://manuall.co.uk/miscellaneous/watches/sekonda-watches/

Click here and also click the images tab.

https://www.google.com/search?q=Sekonda+analogue++digital+watch,+set+analogue+hands

..

Send it to Sekonda for service.

I assume you mean a Sekonda watch.
Watches from large scale manufacturers like Sekonda come with a wide range of glass sizes. 30mm diameter is a common one, but you would need to remove the glass in one piece to measure it. Watch glasses are commonly in 0.5mm steps (e.g. 30.0mm, 30.5mm,31.00 mm etc.) and may have rounded or bevelled edges so it is often very difficult to determine the exact size without removing the glass.
Additionally, there is the thickness of the glass to consider.
Finally, the 'glass' may be plastic, mineral glass or sapphire crystal.
All in all, you will have to know how to remove the back of the watch, how to remove the crown and stem in order to remove the movement, how to remove the glass in one piece, how to fit a replacement glass, how to refit the movement, how to refit the crown and stem and how to refit the back.
Alternatively, take it to a watch repair centre - you'll still have a working watch after they've finished with it.....

If it is indeed a screw type back it will have indentions ON the back (6 to 8). A special tool is required to remove the back without damage to the watch back. Any reputable jewelry store should be able to remove the back. If there are no indentions then it should be a pop back. Some watches do not have a slot to slide a pry tool under the back. You have to use a sharp knife..taking appropriate safety precautions.

Hello I can't change the time on the digital part of my sekonda 03721 model how can I do it

mcdevito75 here, Generally thr back is simply pryed off useing a sharp knife (steak) or with a case opener, or at times the back is screwed on, little square holes around the back of the watch require a special tool, or there may be 4 screws holding down the back to the case, even if you get the back off you may need Jewelers screwdrivers to remove / replace the battery. BEST BET, look for a small watch repair shop in your area.