Setting Units To Attack

I've just about completed making a 5v5 Hero battle map and I'm on some of the last parts. Now, I know how to spawn units, but I need to know how I can make those units move and attack.

I want them to attack prelimenary defenses (towers) and attack enemy units if they encounter them on the way there. Then I want them to move on to the next set of towers and finally the main base.

Action - Pick all units in (leftspawn) and do order (picked unit) to attack-move to center of region 0001.