Hi,
You need to setup some states or conditions to emulate intelligence for each of your enemies then use these conditions to control what each one does. E.g:
if enemy(x).state = 1 then it stands() around doing nothing
if enemy(x).state = 2 then it chases() the player
if enemy(x).state = 3 then it fires() at the player
if enemy(x).state = 4 then its dead
etc, etc....
Use each state to access a different function which control the actual actions of each enemy.
You can set up as many variables and conditions as actions you want each enemy to do.
Theres a lot of good and basic examples been posted in the forums. Do a search for AI.
Good luck.