Mupen64Plus and how it works with downloaded games

I have several problems:

1: I have never utilized an emulator of any kind, nor have I utilized any games related to the ones found here.

2: I have been successful in installing Mupen, and opening the two games I downloaded, but functionality is limited, exceptions and crashing occur often and I cannot seem to set up a functioning control setting. I would love to be able to utilize my mouse for looking about, and selecting items, but I'm not sure this is possible.

So, the problem isn't that the programs aren't functioning, I just don't know how to use them.

If anyone has the time to post a few helpful steps, that would be great.