Measure the length of snap lock duct pipe you need. Cut it with your aviation snips to the measured length.
Grasp the snap lock pipe at one end and begin snapping it together. It snaps together by inserting the male part of the seam into the female part. Keep moving slowly down the pipe working the seam together. As you get toward the end, it should all completely snap together.
Crimp one end of the pipe with your pipe crimper to make it ready to assemble. Repeat the above steps until all your duct is assembled.