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 recording, click the Stop button in the menu bar or press Command + Control + Esc
Open the saved file from the chosen location
Alternatively, open QuickTime Player
Click File
Click New Screen Recording
Click the Record button
Select the screen area or record the entire screen
Click Stop to finish recording