Brother MFC-8510DN Basic User's Manual page 76

f
Pull off the protective cover.
Important
Put the toner cartridge in the drum unit
immediately after you have removed the
protective cover. To prevent any
degradation to the print quality, DO NOT
touch the shaded parts shown in the
illustrations.
68
g
Put the new toner cartridge firmly into
the drum unit until you hear it lock into
place. If you put it in correctly, the green
lock lever will lift automatically.
Note
Make sure that you put in the toner
cartridge correctly or it may separate from
the drum unit.