Putting up the ridge board
The ridge board needs to be positioned so that the rebated parts at each end sit on top of the apex of the front and rear wall.
This is best done by fixing a couple of galvanized hurricane ties to each end of the ridge board, in line with the beginning of the rebates.
It is now an easy matter to fix the ridge board in place, by nailing through the hurricane ties into the inside-top of the front and rear walls.
Fixing the fly rafters
Fix the four made-up fly-rafter, block, and common-rafter combinations (the units that look a bit like a ladder) in place.
This is best done by sitting one unit (fly-rafter, block, and common-rafter combinations) on one side of the rear wall top plate, so that the top of the rafters (fly and common) are up hard against the ridge board, (with the tops of the rafters being flush with the tops of the ridge beam, and the outside of the fly-rafter being flush with the end of the ridge beam).
You may need somebody to help hold it in place while you nail.
Nail through the ridge beam into the ends of the rafters. Do the same on the opposing side of the rear wall.
Ensure the rafters are parallel with the top plate and then nail (toe nail, angle nail) through the blocking into the top plate to fix.
Likewise with the front wall.
Adding the common rafters
Now add the rest of the common rafters evenly spread out along the ridge board. They should be approximately 16" (400mm) O.C. (crs.)
First nail them to the ridge board. Then run your eye along the ridge board and the side-wall top plates.
Ensure they are straight.
Fix the lower end of the common rafters to the side wall top plate by angle nailing (toe nailing) through the side of the rafters into the top plate.
Just one nail at each meeting to hold.
Then fix hurricane ties or similar fasteners to the rafters and the inside-top of the side walls.