Make sure your iPad and Mac are signed in with the same Apple ID
Turn on Wi-Fi, Bluetooth, and Handoff on both devices
On your Mac, click the Control Center icon in the menu bar
Select Screen Mirroring
Choose your iPad from the list
To use Sidecar, open System Settings on your Mac
Go to Displays
Click Add Display
Select your iPad
On your iPad, tap Trust if prompted
Use the sidebar and Touch Bar controls if available
Drag windows to the iPad to extend your desktop
To stop, open Screen Mirroring or Displays again and disconnect
For a wired connection, connect the iPad to the Mac with a cable before starting
Make sure both devices meet Apple Sidecar requirements
Use a third-party app if your Mac or iPad does not support Sidecar