Instructions
Switch into editor mode after loading a Forge map. Press start to open the Forge menu. Select "Change Game Type," which will allow you to scroll through the game types and select the one you'd like to edit.
Navigate your crosshair over a goal object and press "X." This will allow you to scroll through and change properties of the object. You can change an object's team affiliation (for Capture the Flag), radius (for King of the Hill), spawn order (for VIP Escort) and spawn point (for Assault or Capture the Flag).
Save the map after editing the goal objects. If you accidentally delete a goal object, it will re-appear when you save. The Forge will not let you play on an illegal map.