How to record system sound and microphone sound at the same time?

1. Go System Preferences -> Sound.
2. Click
Input and choose Internal Microphone.
3. Click
Output and choose Multi-output Device.
4. When you prepare to record, open Filmage Screen, select an area, then choose
Aggregate Device in audio sources.
There we recommand that you use
external microphone rather than Internal Microphone.

Click Here to learn more about how to create Aggregate Device and Multi-output Device.