When you’re facing the unit with the display screen towards you, you will see the small door at the bottom for the paper tray, a small door above that, and the Xerox logo at the top of the small doors. Along the side of the machine where the small doors attach, you should find an indented handle on either side of the machine.
Gently pull on both handles and this will open the machine and display the ink cartridges already inside the machine.
Gently slide out the old cartridge you wish to replace and slide the new cartridge in the same way the old one went out. There should be arrows on the cartridge itself to indicate the proper way of replacing it if you forget.