Go to the Actor Classes viewer
Go to Pawn - CTPawn - Republic - CloneTrooper and select CloneTrooperTM
Right-click the floor next to where your squad starts and choose Add CloneTrooperTM Here
Double-click the trooper to bring up the CloneTrooperTM# Properites window, and click on AI
Set both bCanBeSquadMember, and bOfSquadInterest to true
Save, and boot up the level.