How do I replace the toner cartridge?

First, power on the printer and open the top cover until it locks in the open position. Push down the lock lever and remove the old toner cartridge from the drum unit. Unpack the new cartridge, remove the orange protective cover, and shake it 5 to 6 times to distribute the toner evenly. Insert the new cartridge firmly into the drum unit until the lock lever locks automatically, then reinstall the assembly back into the printer.