How do you program a westinghouse model TM236 timer?

It's simple. There are 3 button to the right of the display (Time, On, and Off). To set the current time, press and hold the Time button and then set the time using the Hour and Minute buttons to the left of the display. To set when you want the timer to go on, press and hold the On button and set the time with the Hour and Minute buttons. To set when you want the timer to go off, do the same as above, except press and hold the Off button.

Now to turn the timer on, just move the switch on the top to Timer.