Most of our heat pumps (apart from mini heat pumps like the Hot Splash and Sunspring models) include a water flow switch. This means that they will only operate when your pool pump is turned on and water is flowing through the heat pump.
You can therefore control when your heat pump operates simply by using a time clock on your water pump.
Some heat pump models also have a timer built into the digital control panel. This allows you to turn the heat pump on and off at set times independently from the pool pump. Note that the pool pump always needs to be operating for the heat pump to work.