Welcome to BYC, if you can give us a picture of the shed and demotions that could help us give you suggestions, remember not all you have to do, but the more options to pick from the better you can make your coop, I don't know how many chickens you have/are getting but a good rule to go by is a min. of 4 square feet per bid in the coop, a great thing is a poop board you can scrape it off or use sand or PDZ but it will keep your floor a lot cleaner, use 2X4 for roosts that way they are wide enough so there aren't any frostbit toes this winter, for my set up I will have nests in two rows and they will be 1X1X1 and with two that puts your poop board at 2 feet your lowest roost at 3 feet and if you stagger 3 roosts you can get your highest roost to be about 5 foot.