Dell 5100cn Color Laser Printer User Manual page 201

1. Select the new toner cartridge whose color matches the cartridge carrier and remove it from its packaging.
2. Shake the toner cartridge several times as illustrated to distribute the toner evenly.
3. Align the toner cartridge with the corresponding cartridge carrier in the printer and insert it.
4. Grip the levers at each end of the toner cartridge with your fingers, then push down firmly to rotate the levers
forward.