Change a user’s picture on Mac
You can change the picture that appears next to a username in the login window.
On your Mac, choose Apple menu
> System Preferences, then click Users & Groups.Click the lock icon
to unlock it.Enter an administrator name and password. You can change your own picture without unlocking Users & Groups preferences.
Select the user account on the left, then click the picture on the right.
Instead of clicking the picture, you can drag an image file from the Finder
onto the picture.If other users are logged in to this Mac now, you can’t select them.
Do one of the following:
Use a picture included with macOS: Click Defaults, then select a picture.
Take your picture using your Mac: Click Camera; when you’re ready, click Take Photo.
Use a picture from the Photos app: Click Photos. To see specific photos from a time, place or album, click a disclosure triangle below photos, then select a group of photos. Select a picture, then click Next.
Adjust the picture.
Zoom in or out: Drag the slider left or right.
Move the picture: Drag the picture around within the circle.