HP OfficeJet Pro 7740 - Manual (Page 108)

2. Open the cartridge access door.
NOTE: Wait until the print carriage stops moving before proceeding.
3. Press the front of the cartridge to release it, and then remove it from the slot.
4. Remove the new cartridge from its packaging.
5. Using the color-coded letters for help, slide the cartridge into the empty slot until it is securely installed
in the slot.
Make sure that the color-coded letter on the cartridge matches that on the slot.
6. Repeat steps 3 through 5 for each cartridge you are replacing.
7. Close the cartridge access door.
ENWW Replace the cartridges 95