Watch these videos as revision or to clarify further the key concepts in this topic

This video goes through a sample problem on angle of elevation.

Here is a very good video which clearly goes through all the fundamental concepts of trigonometry and SOHCAHTOA in right angled triangles

This video gives a problem using angles of depression and elevation. You should pause the video and attempt to do the calculations  yourself before watching the teacher solve the problem. 

Here is another video with a practice problem on angles of depression which you should use for revision by pausing and solving the problem before you watch the teacher solve it.