Cut out the parts. I might use the gluing tab shown, or cut it off and place it inside. That’s OK for this big one, but for the tiny ones for the actual model I do neither—I just butt glue the edges together. Form both pieces around a mandrel. I find it easier to get a piece of wire the right size, and form and glue the tube right on the wire. It will slide off when the glue is dry. On the small part for the cowl, I used the gluing tab because it is so small it doesn’t show anyhow.