A reset isn't needed on the 1st refill of any original cartridge however to refill the cartridge simply remove the sticker and pull out the plug it was hiding with a screwdriver. Some customers like to airbrush the interior of the cartridge however others simply refill the cartridge with new toner. Replace plug making sure all leaks are sealed (melted wax works).
To RESET the cartridge, go to the other end and take out the 2 screws. Gently take off the end plate avoiding displacing the cogs which are free to drop if you're not careful. Identify the grey lug butted up against the black protusion (which stops it from turning anymore telling the machine its time for a new cartridge). Lift the grey disk and lug minimum necessary to get the lug clear of the protusion and then rotate it anti-clockwise before allowing the lug to fall by itself into the new start position as shown in the image. Replace and screw on the end plate and when replaced the machine will think you have installed a brand new toner cartridge