Brother DCP-8045D - Manual (Page 109)

TROUBLESHOOTING AND ROUTINE MAINTENANCE 7 - 28
4
Gently rock the toner cartridge from side to side five or six times
to distribute the toner evenly inside the cartridge.
5
Remove the protective cover.
6
Insert the new toner cartridge in the drum unit until it clicks into
place. If you put it in properly, the lock lever will lift automatically.
Toner Cartridge
Drum Unit