Canon L90 - Manual (Page 142)

7-5
Maintenance
6
Hold the toner cartridge by its
handle (A).
7
The arrow (A) on the toner
cartridge should be facing away
from you and pointing down.
8
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.
9
Push the toner cartridge to make
sure it is properly set in the
machine.