A:
If you plug an HDMI cable with a signal into your TV, it "knows" there is an HDMI signal present, but it doesn't "know" (or "care") what the source of that signal is. So, on your TV you would select the HDMI jack (HDMI1, HDMI2, HDMI3, etc.) that you plugged into.
Likely you will have to change a setting on your PC to tell it that you want to use an external monitor. You might also have to specify that you want the signal to go to the HDMI jack. (I use MACs more than PCs, so I don't know enough to be more specific.)