Just keep putting them up until they do it on thier own, it shouldn't take too much longer than a week. Going out early and leading them up with treats and putting a little light in the coop for a few days will help speed the process. It's too hot to coop them in right now in 90% of climates. It is a little effort, but it's not forever. If you don't you risk them making a snuggle pile in the corner of the run and making a habit of that, I can't tell if you have hardest cloth on the lower portion of the run or not, and if not obviously things can grab, nibble, or paw at them.