Making an object fly at selected item.

I am making a 3rd person game right now and everything has been going smooth so far. I have a set of spells that the player can use on opponents. For example if I had a fireball spell and i wanted to use it on a selected enemy, when I click that enemy it is "selected" and the fireball will leave the player and fly to the enemy, and if the enemy moves then the fireball continues on in a strait path. I have the selection system done but I don't know how to create an object and have it leave the player headed in a strait path to the enemy. Could somebody help me on this one?