Very carefully (tounge in cheek). If you are going to light and tune it outside the forge put it in your vise. Turn on gas at LOW pressure - use a torch striker or flaming paper in front of the nozzle. If it doesn't want to light turn off the gas, wait til you cannot smell gas anymore, adjust the choke down (assuming you have the choke wide open)and try again. Somewhere in this process it shouild light up for you.