How to record system sound from macbook
You can make screen recordings using QuickTime (https://support.apple.com/kb/PH5882?locale=en_US) or 3rd party software such as ScreenFlow (https://www.telestream.net/screenflow/overview.htm)

I prefer ScreenFlow because it's so customizable, is more akin to movie editing software than anything, and the exported video files can be compressed in many different ways. It also supports recording your iPhone/iPad screen.