Canon L90 - Manual (Page 170)

8-7
Troubleshooting
7
Insert the toner cartridge so that
the guide (A) on the left side of the
toner cartridge fits into the groove
inside the machine and slide it
down parallel to the guide.
8
Push the toner cartridge to make
sure it is properly set in the
machine.
9
Close the toner cover.
Be careful not to get your fingers caught.
10
Open the paper delivery tray (A)
and the extension (B).