To set up your level for Capture The Flag ...

F6 = LEVEL PROPERTIES

In the LevelInfo rollout TYPE this:

XGame.xCTFGame

Right click on the floor surface wherever you want the red or blue flag.

Make player starts around the bases so the blue guys spawn by the blue flag, etc:

In the PlayerStart tab set the team number for each player start:

0 = red team
1 = blue team