First, you must ensure you are away from any flame since lighter fluid is highly flammable. Then remove the inside unit from its case and turn it upside down. Lift the corner of the felt pad on the bottom of the insert to reveal the packing material in the fuel chamber. Slowly fill the lighter and saturate this packing material with lighter fluid. Stop filling the lighter when the fuel reaches the top of the packing material. Do not overfill. Once finished, insert the unit back into the case and be sure to wipe off all excess fluid from both the lighter and your hands before igniting the lighter. A demonstration of this process is provided for you in the video below.
For Zippo Windproof Lighters: Remove the inside unit of your lighter and find the flint spring on the bottom of the unit. Being careful so the spring doesn't fly away, use a small screw to remove the spring. There is a brass tip attached to the end of the spring, this is not the flint. Turn the lighter right side up and gently tap it against a hard surface to remove the remaining piece of flint. Insert a new flint into the tube you pulled the spring from. Replace the flint spring and screw it in. Replace the inside unit into your lighter case. A demonstration of this process is provided for you in the video below.
For Zippo Blu Lighters: Remove the wheel cartridge by pulling it straight up. Turn the cartridge upside down and remove the screw with a small screwdriver or coin. Doing so will also remove a long spring with a brass tip on its end. Remove any remaining old flint and insert a new flint into the tube. Replace the spring and screw, making sure to tighten the screw securely in place. Replace the wheel cartridge into the lighter with its notched side facing the burner. A demonstration of this process is provided for you in the video below.
How do I replace the wick in my Zippo windproof lighter?
When the wick of your lighter becomes black with carbon, pull it up with pliers until clean wick appears and cut it even with the chimney. When the wick needs to be replaced, remove the lighter's inside unit and use tweezers to remove all of the packing material in the fuel chamber. Insert a new wick through the chimney and pull it through the insert with tweezers. Replace the packing material in small pieces, interweaving the wick in between the padding pieces. Trim the wick even with the chimney and replace the inside unit into your lighter's case. A demonstration of this process is provided for you in the video below.