Dell C3760dn Color Laser Printer - Manual (Page 335)

Maintaining Your Printer 333
4 Insert the used waste toner box into the plastic bag that came with the new waste toner box and seal the bag.
Installing a Waste Toner Box
1 Unpack a new waste toner box.
2 Insert the waste toner box.
3 Turn the waste toner box lock lever 90-degrees clockwise to lock the waste toner box.
4 Close the right side cover.