To fill a Zippo lighter, take the lighter out of the case and turn it upside down. Open the can of lighter fluid and turn it upside down, touching the nozzle to the cotton that is exposed on the bottom of the lighter. Squeeze the can until you see the cotton interior of the lighter being saturated, then stop. Insert the lighter back into its case while it is still upside down, then turn it upright and test it out! If you get any of the fluid on the flint, it might take a few minutes before it will light.