Here are videos from the Tower Garden company to help you setup your Tower Garden for the first time.
This video covers adding water, nutrient solution, and setting the timer.
Since I mostly grow indoors, I use a 2 gallon watering can instead of a garden hose. The video will tell you to set the timer at 15 minutes on, 15 minutes off. For indoor growing, this should be 15 minutes on, 45 minutes off because the rockwool won’t dry out as much indoors as it will outdoors.