Oki 87 - Manual (Page 29)

Installation 17
7 Remove the toner cartridge from its package and gently shake it
from side to side to distribute the toner. Then carefully peel the
white plastic tape from the bottom of the toner cartridge.
8 With the ridged side facing up and the gray lever on your right,
insert the toner cartridge into the image drum unit. Slide the left end
of the cartridge in first, then lower the right end into place.
Warning: Be careful not to insert the toner cartridge backwards
into the image drum unit.
9 Once the toner cartridge is in place, push the gray lever all the way
forward to secure it and release the toner.