If you want what i think you want, then you dont need scripting, just world builder.
place your "enemy" units and stuff, then your units, then goto
Edit>Player List, and select the civilian faction, or the faction you chose to be your enemy, and select your faction in the "enemies" box.
There, you have your enemy.
If you want them to rush into you, then all you have to do is place way points and assign each unit to a waypoint(or multiple units).
Dont ask me how to do the waypoint thing ^^