How do you rotate a point other than the origin? Can you give me a video or explain it?

what you do is translate so that the desired point becomes the origin. Then rotate as usual, and undo the translation afterwards. Each of these operations can be described using a matrix, and the whole shebang can be performed at once by using the product of the three matrices to operate on the new coordinates.

Any good computer graphics text will explain this, and I'm sure youtube has videos as well.