Detach the key-chain ring from the top portion of the canister, if needed.
Hold the bottom portion of the canister with one hand.
Grasp the "Zippo" branded top-collar with the remaining hand. Unscrew and remove the top-collar, using a counterclockwise motion. Be sure to hold the canister appropriately to avoid spilling any residual fuel present inside.
Extend the Zippo lighter fluid spout, located on top of the can.
Fill the canister with an adequate amount of lighter fluid. Do not fill the canister completely to the top, as this will increase the chances of spilling the fluid.
Screw the top of the canister on to the main body, using a clockwise motion. Check the tightness of the top cap and top-collar to complete the process. Close the fill spout on the lighter fluid can.