Facecam options differ depending on the editing program you use.
Click New Movie Recording.
Position your face cam at the top center of the screen.
Minimize Minecraft so we can see your face as you play.
In the Sources panel, click the plus button and add Video Capture Device.
In the pop-up box, click Add Existing and choose from your options. Otherwise, click Create New and click OK.
Then, under Device select your webcam and click OK.
In the Sources panel, move the Video Capture Device to the top of the list.