Turn on the Nintendo Switch
Open the Controllers menu on the Home screen
Select Change Grip/Order
Turn on the controller you want to connect
Press and hold the Sync button on the controller
Wait for the controller to appear on the Switch screen
Release the Sync button when connected
Press any button on the controller to confirm it works
For wired controllers, connect the USB cable to the dock and controller
Make sure the Switch is docked if using a wired connection
Repeat the steps for additional controllers