Dell 3100cn Color Laser Printer - Manual (Page 198)

5. To insert the toner cartridges, align the arrows on the cartridge with the corresponding arrows on the printer. Guide the cartridge in until it snaps into
place and then push down the handhold to lock the cartridge in place.
6. Close the front door.
7. The toner cartridge carrier rotates to the next empty slot. When the color of the newly inserted cartridge appears on the display, followed by the Insert
message, insert the next toner cartridge.
8. Repeat steps 1 through 7 when inserting the remaining cartridges.
Installing the Drum Cartridge
1. When the Insert Drum or Insert Drum Cart message appears, open the front door, then lift and push back the top cover.
NOTE: Make sure the toner cartridge is installed correctly. Otherwise, the front door cannot close firmly.