They make controllers to handle multiple lights. Or you could plug them in seperate outlets with seperate timers, or a strip to a timer like I do.
Depends on what power lights.
On a 110V 15amp you could run 3 400w, or 2 600w, or 1 1000w.
On a 110V 20amp you could run 4 400w, 3 600w, and 2...