O.K., I downloaded the report but only looked at it briefly. I think a Pilots operation book would be satisfactory. The Flap Selector Handle is in the upper left of the picture and very difficult to see. The flap actuator which actually would move the flaps is probably hidden in the upper fuselage somewhere.
The pilots view of this center portion of the overhead panel would be different than the picture. If the picture was rotated 45° clockwise, it would be more accurate.
Try this link:
cockpit photo twin otter - Google Search
and
Cockpit Overhead Panel - 8Q-TMQ | Flickr - Photo Sharing!
Note the small square thing at the aft end of the handle. That thing has to be pushed(normally your thumb is used) to unlock the handle in order to move the handle for a new selection.