They're pretty simple. The vent screws to the roof around the perimeter of the flange. Maybe 12 screws total. Use sealant under the flange, around the perimeter, and on top the screws.
There is generally enough give in the curved aluminum roof to conform to the flat flange. It's probably not necessary, but I used a piece of aluminum angle on the front and rear edge of the flange to help flatten the roof. It's installed below the exterior skin, so the flange screws go through the flange, then the roof, then into the supporting angle which is hidden in the ceiling. There are pictures on our blog if you care to see what I did.
Connect the two 12v
wires to your electric, install the interior trim, and you're done. I installed Maxxfans, not Fantastic fans, so I didn't have the option of a curved interior trim. The flat trim looks fine.