Option 1 - Click the Control Center icon in the menu bar and click Screen Mirroring.

Option 2 - Turn on Mirror in System Preferences
- Go to Apple > System Preferences > Displays
- Select Display settings, then click on Use as: and see if you can change the desired display to Mirror.
!["use as" menu up with "Mirror for [other display]" highlighted](https://td.cscc.edu/TDPortal/Images/Viewer?fileName=10f123d5-140b-44cc-9d4e-64aa440bd24d.png)