After plugging in the timer, press the Program button until the desired function appears in the LCD screen. The choices include O (Always On), f (Always Off), 1-9 (on at dusk and off after the set number of hours), R (on at dusk, off after a random length of time) and d (on at dusk and off at dawn). The manual for the Woods 50013 outdoor 24-hour timer is available here:
http://waterheatertimer.org/pdf/Woods-50013.pdf .
I hope this helps.
Cindy Wells