Hey Paul,
The best advice is to follow the tutorials because they will answer your question and you will also learn a couple of other tricks that are vital to know when you begin.
But to answer your question, give your enemy a movement tbehaviour (bullet for example), set the speed of the object to 50 or whatever you want and then have an action that sets the angle of the object to face your desired object and they will hone in on him.
If any of that doesnt make sense try the tutes ;) you will be surprised how quickly you pick everything up.