Targeting (noob question)
If it helps, you can target an enemy by using the “Tab” button on your keyboard, which will select the closest attackable target (although caution, this will also target passive enemies).
I believe you can also change the options so that when you use a damaging skill, it will instantly lock onto the nearest attackable enemy as well (though, that option might be turned on by default, I can’t remember).
Once you have the target you want to keep attacking, hit CTRL-T. That puts a red targeting circle over its head. Until it dies you can reacquire it if you lose target (sadly very easy to do) just by tapping T. If you are in a party, the CTRL-T shows the target circle to everyone, and each party member can move it by CTRL-T’ing a different target or acquire it for themselves by tapping T.