how do you make the ply wood bend

This is 3/8th plywood and probabley like you, I though it would ben way easier than it did, it was only 5 feet long and I had to cut it in 3 different parts otherwise It would have broken. You can see one part were their is a tinny gap, those are 2 different peices and now I have put the 3rd one on. Also, even once you have smaller peices it won't just bend, you have to put the screw through and get it into the 2 by 4 underneith and then the plywood will bend from the force of the screw.