To record your screen on Mac with voiceover, you can use QuickTime Player, a built-in app on all Macs.

Here are the steps:

1. Open QuickTime Player.
2. Click File > New Screen Recording.
3. In the screen recording options, click the Microphone dropdown menu and select the microphone you want to use to record your voiceover.
4. You can also choose to record a specific portion of your screen by clicking and dragging the selection box.
5. Once you’re ready to start recording, click the Record button.
6. To record your voiceover, speak into the microphone while you’re recording your screen.
7. To stop recording, click the Stop button in the menu bar.

Your screen recording will be saved to your desktop as a .mov file. You can then open and edit the recording in QuickTime Player, or share it with others.