Dell 3100cn Color Laser Printer - Manual (Page 199)

2. Remove the protective sheet from the drum cartridge.
3. To insert the drum cartridge, push up the lever on the right side of the printer. With the lever in the upright position, hold the drum cartridge by the
handle, align the arrows on the drum cartridge with the corresponding arrows on the printer and guide the cartridge in until it snaps into place.
4. Pull down the lever on the right to lock the drum cartridge in place.
5. Close the top cover, then the front door.