The internal components of the HP 6122 printer are held together by a metal chassis. The ink cartridge can be found inside the printer.
Check to see if the printer is on by identifying whether or not the bottom button on the right face of the computer is green. If button is green, proceed. If not, check guide regarding "Turning on Printer."
Lift open the front panel to gain access to the inside of the computer. Upon doing this, the printer should respond by moving the print cartridges more toward the center.
Notice the ink cartridges located in the center of the inside of the printer. Note that the larger cartridge on the left holds the colored ink, and the thinner cartridge on the right holds the black ink.
Remove the color ink cartridge by lifting back the teal plastic cover located on top of the cartridge. Proceed by repeating this step from the black ink cartridge. Then grab the pertruding part on the top of the cartridge, and lift cartridges gently out.
Finish installing new cartridges by shutting front panel. Upon doing so, the printer should react by moving the cartridges back to where they started (not visible since panel is closed, just listen for it).