There should be a small metal electrical switch box with a hinged cover(waterproof),inside you will find the switch(two switches if you have a pool light built in). There also should be a timer inside a plastic or metal electrical box near your electrical power breaker box(power main).(mine has INTERMATIC stamped on cover) Inside will be a dial like a clock with two pegs one for start time and one for end time, adjust these to your desired on & off times. There is a metal lever or switch, turn to right for on,left for off. If it is working properly both power switches should remain ON and your pump should turn on and off automatically everyday at the times you have set P.S. ,It is recomended by manufacturer to run it at night and off during the day,also size of pool and water temperature are used to determine how long to run your pump. You can call or visit your local pool supply store for advice they will be happy to help you out. have pump & filter brands & model #s handy before you call, timers also.
Hope this helps and not too confusing, Good Luck.