You need to:
- Open the SmartThings app, go to add (+) > device
- Click on “Scan nearby” and put your device in pairing mode.
Note: You can also select the device from the device catalog if possible - There, you should see the device was discovered, after that, wait a few seconds (so the joining process is finished).
Note: If you see the device wasn’t paired correctly (the device was created but you’re not receiving events - for Zigbee mostly), try to pair the device again and wait a few more seconds in the “scan nearby” page. - Go back to the devices list and you should be able to find it there, it might be in the “No room” section