I have one that I use. First empty the tank if it has anything in it and rinse it out well with a little gasoline. The pump on most of them can be removed with a wrench. Usually the leather seal on the pump is dried out. If it's not too bad you can soak it with a little light oil and it will swell up and work. If not you may have to make a new one. I took the valve and needle apart and cleaned them up on mine. They work just like an old Coleman camp stove. Fill the tank up about 2/3 full of unleaded gasoline and pressurize the tank with the hand pump. TAKE IT OUTSIDE BEFORE YOU TRY TO LIGHT IT!
On mine there is a little trough under the burner/valve assembly. Open the valve and let a little gas drip into this reservoir and light it, carefully! The fuel burning in this trough helps preheat the burner to atomize the fuel. Slowly open the valve and let it burn in a safe direction as it heats up. As it heats up it will turn from a yellow to a blue flame as the preheat fuel burns up. They are kind of scary the first time you use them. I like to keep a fire extinguisher close by. You might have to add pressure to the tank after it burns a little while. They usually have a little bracket on top to support an old fashioned copper solder iron while it is heating. I used mine a while back to heat my irons while I soldered a gutter trough together on a job. You use two irons, keeping one heating on the torch while you use the other.