OK....to check the gauge, remove the wire from the sender and ground it to the engine block,or cylinder head, now turn on the ignition to the on position the gauge should read at the top of the hot scale....if not then you need to first check the the is power to the gauge, check the continuity of the gauge to sender wire, if those check ok, you then either replace or fix the gauge.
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"