Turn on your PS5 controller by holding the PS button and Create button until the light bar flashes
On your Steam Deck, open Quick Settings
Go to Settings
Select Bluetooth
Turn Bluetooth on
Choose Add Device
Select your PS5 controller from the list
Confirm pairing if prompted
Wait until the controller shows as connected
Test the controller in Steam or a game
To reconnect later, press the PS button on the controller
If needed, disconnect and re-pair the controller from Bluetooth settings