I've never seen or used that type of hinge but it looks to me that you would position the flaps in the "up" position and temporarily hold them in place, such as with tape. Cut slots on the bottom near the wing trailing edge and flap leading edge corresponding to the location of the hinge tabs, with the pivot point centered above the trailing edge of the wing. There should be material (usually hard balsa) in the wing and flaps where each hinge attaches and one of the hinges should line up with the flap servo arm (make sure the "control horn" is on the flap side). You can cut off the upper "control horn" portion of the other hinges. Leave a little extra open area around each hinge opening, fill it with Aeropoxy or similar, and slide them in place, making sure they are perpendicular to the wing/flap and in line with each other.

Because the hinge pivot point is "offset" below the flap centerline, it creates a down and aft movement of the flap versus just down. This more or less emulates a Fowler flap and theoretically increases the wing area, making the flaps more effective.

Actually, those hinges look pretty clever and should be fairly easy to install. Hope this explanation makes sense.

Craig