The same question seems to be coming up a lot lately, "Ryan, how can I create a video that records my screen while also recording my voice?" It's called screencasting, and Screencastfy is a free Chrome extension that works perfectly to get this job done.
This post contains a video that explains what a screencast is, why you might want to screencast, and how to screencast. You will also find a Google Slide show that shows how to install Screencastify and begin recording with Screencastify.