Its in the effects pull down menu. I think it may be called FLOP. If it is not FLOP then its there in the effects menu somewhere. In the manual it will tell you what each effect does but I am thinking it is the FLOP one.
I am pretty sure the effect is called "mirror." As Shooter said, it is in the effects menu under a submenu that is in "video filters." Just look around, it is in there somewhere.