FPS Beginner Help

I am working on an FPS game. I was working if someone could point me in the right direction here. I created a model of an enemy and placed it in my game world. I can move around just fine. How do I make the enemy "see" me.

look up the following commands they may help:
entitypickmode
linepick
entitydistance
enttyvisible

In the code archives are some useful functions that determines visibility.

http://www.blitzbasic.com/codearcs/codearcs.php?code=532
and
http://www.blitzbasic.com/codearcs/codearcs.php?code=871

thank you so much