When I record anything or share my screen on my iMac it only shows my mouse. What am I doing wrong/how do I make it show the rest of the screen too?

I am trying to record my screen on my iMac for a youtube video. I am using Debut (a screen recording program) and whenever I record the screen, the resulting video is always only showing my mouse movements and not anything else i.e the actual windows etc. This also happens when I share my screen on skype! How do I make the other parts of the screen show up and what am I doing wrong?!

Thanks!