how do you set the timers?

There is only one timer and if you read the directions it tells you how to set it.

There are mechanical slides at 15 minute intervals around a 24-hour dial - you slide each one to either the on or off position - much like a mechanical timer.

Simple trip switches for every 15 minutes: either off or on. Set when you want it to come on; for 15 minutes every 24 hours or 15 minutes per hour all day or part of the day. You can even set it to always on, always off or use timer with another separate switch.