I've been watching several Let's Plays recently, and I thought that I'd like to experiment by making my own. But I'd like to do one that includes my own commentary, with me talking through a microphone while playing and recording the game. I don't know how to do this.

Also, I've been trying to make preliminary video recordings using DOSBox. However, as I'm using Ubuntu, I've had to remap the video recording keys to something like CTRL+ALT+R. I press the buttons, start playing for just a couple minutes, but when I exit and try to find my recording there's no sign of it. Anywhere. Is there something I'm doing wrong here?