The drum unit is the gray bottom half of the component in the picture, while the top black part is the toner cartridge.

Separate the toner cartridge from the drum unit by pressing down on the blue tab and gently lifting the toner cartridge up by the lift on the handle.

DO NOT TOUCH the roller bar on the toner cartridge, or the roller bar on the drum unit as illustrated in the pictures. This may cause a decrease in print quality.