Here's how it goes:
1. Make a Colonel X and create the waypoint he will follow.
2. Right click on him and change his name from Colonel X to Bob.
3. Place the trigger zone where you want the player to walk through.
4. Right click on the trigger zone and in the Main AI section, change plrinzone.fpi to plrinzoneactivateused.fpi.
5. In the IfUsed section put Bob.
6. Right click on the Colonel X again, and under the respawn section, change spawn at start to no.
7. Then change the 2 first zeros to ones.
Exit, test your game, and when you start, and step into the trigger zone a Colonel X will spawn from nowhere and follow a waypoint.
I hope that was what you're looking for.
Give a man some bullets, and he'll want a gun. Give a man a gun and he'll be giving away the bullets!!