Right you plug the flylead into your rear hydrovane channel on the receiver. Connect the servo lead to the pins underneath the flylead on the APC-4. Observe polarity.
If memory serves me well, the medium jumper setting is best for your boat, but it'll be a case of suck and see.
Once you've done this, and have tested it working, fix the APC-4 to spare space on the equipment tray- observe you have it the correct way around.
Adjust the level pot with the aid of a small screwdriver and spirit level. Job done.