First locate the refill nozzle and flame adjustment screw.
Drain all existing fuel from the lighter using a pen, small screwdriver, or some other small pointed object by depressing the fuel refill nozzle. Turning the lighter right-side-up with refill nozzle pointing toward the ground helps get the last bit of air out.
Turn the flame adjustment screw all the way clockwise to shut off all fuel flow
With the fuel nozzle on your lighter pointing up, press the can of fuel into the lighter with the fuel can nozzle pointing down. Be patient, a lighter does not become refilled in 2 seconds. Do not pump the fuel can into the lighter. On some of the less expensive lighters, this could cause the tank to repture.
After refilling , let the lighter rest until it reaches room temperature. The fuel is cold when refilling and will expand as it reaches normal temperatures.
Turn the flame adjustment screw 1/2 turn counter clockwise and try to light the lighter. Keep turning the screw in 1/4 turn increments until the lighter lights. Make minor adjustments as necessary. Try lighting a couple of times between adjustments.
A few tips and tricks
Use only triple refined ( or higher ) butane fuel. Sometimes when the lighter will not ignite, blow sharply into the flame mechanism, or used compressed air. This will sometimes remove small particles of dust and dirt, which will render your lighter useless.
For faster refilling, place your lighter in the freezer for a few minutes. A cold lighter will actually suck the fuel from the can and will refill faster.