Just go Search for Tutorial on How to make a TD (Not for the tower but only for the creep,.. its the same system) and for the mouvement trigger:
Event
Unit - A unit enters Region 012 Copy 4 <gen>
Conditions
(Owner of (Entering unit)) Egual to Player 12 (Brown)
Actions
Unit - Order (Entering unit) to Attack-Move (Center of Region 004 <gen>)
Event
Unit - A unit enters Region 012 Copy 4 <gen>
Conditions
(Owner of (Entering unit)) Egual to Player 12 (Brown)
Actions
Unit - Order (Entering unit) to Attack-Move (Center of Region 004 <gen>)