The leading edge has to be squeezed together to fit between the nose ribs and the projecting tangs on the main ribs. It doesn't require much force, but the length of the components make it a bit tricky if working on your own. I was going to ask someone to lend a pair of hands, but I found that long thin cable ties solved the problem. Just make sure the heads of the ties are not on the inside, as you need to get them out once it's put together...