Dell 3010cn Color Laser Printer - Manual (Page 120)

5. Lift the tab up 90 degrees and pull the toner seal straight off, keeping it parallel with the toner cartridge.
6. To insert the toner cartridge, face the label on the cartridge to the front and align it with the arrows on the printer.
Inserting the cartridge
a. Guide the cartridge until it snaps into place.
b. Push down the handhold to lock the cartridge in place.
NOTE: Make sure that the printer is turned on.
CAUTION: Do not do not force the cartridge.