Press Shift + Command + 5
Choose Record Entire Screen or Record Selected Portion
Click Options to set microphone, save location, and timer
Click Record
To stop, click the Stop button in the menu bar
Open the saved video from the location you selected
Use QuickTime Player if you want another built-in recording method
Open QuickTime Player
Go to File
Select New Screen Recording
Click Record and choose the screen area
Click Stop in the menu bar to finish
Save the recording when prompted