So simple to install and you would never ever know it was made from styrofoam!!  I am very pleased!   Put in a spare room to experiment for starters.   Have already ordered more to put in a quest bedroom!  I never dreamed covering a popcorn ceiling could be this easy.  I used Gorilla Glue Heavy Duty Adhesive in caulk form.   Drew a bead 3/4 inch from the edge around the outside and crisscrossed through the center.  These are so so lightweight it doesn't take a lot of adhesive.  Easy to do by yourself.  Cuts easy with an box cutter or exacto knife.