I still have one of those around here somewhere. I used one a lot in the military and used one for backpacking in the early '70's. What you do is pump it up, open the valve part way to let a little fuel escape then close the valve. Light the stove and let it warm up by burning the released fuel and then slowly open the valve again, the desired flame is blue, solid without flareups and yellow flame.
I would be careful, those stoves are almost always really old and the gaskets may all be shot. If anything seems to leak, forget about lighting it up! Hope that helps some. Good luck.