First check the coolant level before starting it. I bet it's low...top it off...
Don't let it idle with out keeping an eye on the gauge. If it gets to 3/4 of the way up, try touching the upper radiator hose. Don't get burnt!!! and don't stick you hand in the fan!!! If you can touch it, then check the thermostat housing. Your hands can't handle temps that are truely above half way on the temp gauge. If you can touch those two and the valve cover the engines probably not overheating it is seeing steam at the thermostat.
You are best off to not let the gauge get into the red. If it gets hot, let it cool off and add some coolant. When it get's half way rev it a little bit to move the water through the engine to flush out the air
Report back exactly what you see, did and how you did it. We will go from there...