Programming enemy AI can be *really* difficult. There are a lot of different ways to go about it, and it all depends on if your games is a sidescroller, top down, what you want the enemies to do, etc. AI can be as simple as making the enemy always head towards you, to as complicated as making the enemy plan a route and strategy to try and catch you off guard. If you want any help, you're going to
need to be more specific than just asking how to make enemy AI. We would need to know what exactly you wanted the enemies to do. I recommend giving it a shot yourself before asking for help, too, as finding out for yourself what works and what doesn't is, in my opinion, the best way to learn!