When you connect the controller to your dock, it will immediately be recognized by your Nintendo Switch and show up in the Controller Configuration Settings. If this is not the case, please check if the controller is getting power. You can do this by pressing the function button next to the right analog stick. If you press and hold it for 3 seconds, the LED will now light up. If the LED doesn't light up, check if the cable is properly inserted into the controller and your dock. Also try connecting the cable to the other USB-port on your Switch-dock.