To connect your Nintendo Switch to a TV, place the Switch into the Dock, make sure the Dock is plugged into power and the TV via HDMI, then switch your TV to the correct HDMI input. Your Switch screen should appear on the TV.
To connect your Nintendo Switch to the TV with the Dock, insert the console into the Dock, connect the HDMI cable to the Dock and TV, plug in the power adapter, then select the correct HDMI input on your TV.
Connect the HDMI cable and AC adapter after opening the dock's back. Connect the HDMI to your TV and the adapter to the wall. Lastly, insert the Switch console into the dock and select the appropriate HDMI input on your TV.