Slide the Cokin p filter holder on the adapter ring until it snaps in place. The cokin filter holder is now solidly attached to the lens, yet it can rotate both left and right. Slide the filter into one of the filter holder slots. The one closest to the filter holder housing is the narrowest; it allows the use of round filters with notched edges (polarizer, star filters..). The two central slots are intended for square filters. The outer slot can be used either for an additional filter or for a coupling ring.
Check the back of your lens cap to determine adapter size!