Shut your gas, open the bolt on the bottom and put a can underneath. Then open the bolt at top. Not sure if it's the top that screws off or the bottom (whichever isn't bolted to the wall). Replace the filter with a 10 Micron, close it up, close the bottom bolt, fill with fuel and close the top bolt.
Always put oil pads under your work.
Alternative method: open bolt, light match. Never have to change again.