Finding the angle involves a bit of high-school geometry.

We're going to use simple x and y subtraction to find the x and y distance, then some trigonometry to find the angle.

If you haven't studied trigonometry yet, don't worry about the details too much and just accept it as magic.

If you have studied trigonometry and wondered why people are tortured with such things that hold no relevance to things that matter, now you know -- gaming depends on trig.