Mark the top of the outer walls every 24 inches unless your local building codes require shorter intervals.
Raise a gable end truss so that it rests on the front outside wall. Nail it tomthe wall with 16d framing nails held at a 30-degree angle. For support, nail several 2-by-4s to connect the gable to the front wall.
Raise the other gable end truss so that it rests on the rear outside wall. Nail it the wall with 16d framing nails held at a 30-degree angle. Nail several 2-by-4s to connect the gable to the rear wall.
Lift the remaining gables onto the walls and stack them against the front gable.
Walk a truss to the mark closest to end gable and toenail it to the two outside walls. Nail perpendicular, 1-by-4 bracing strips to the trusses along the underside of the top chords and end gable to stabilize the trusses until you install the roof decking. Repeat until all trusses have been placed.