Timers are used to turn a device on and off on a regular basis. For example, you might want to turn on your irrigation system every ten minutes for five minutes. (On for five minutes, off for five minutes.)
To create a new timer, select "Rules" from the menu bar, "Add Rule" then "Timers." Choose what device will be controlled by the timer. "Time of Day" will restrict the timer to either "Day Only" or "Night Only" or you can make the timer valid "All Day". (Your Day is defined in Settings > Controller Profile.)
Choose "Save" at the top of the screen to save the rule.