What are the most important things I need to knwo about caring for a laying chicken in my backyard?

I have a mature laying chicken. She's in a lattice work garden shed that is covered by jasmine and is about 10 feet by 5 feet. There is a plastic portable "shed" that has 2 shelves and is about 3feet wide, 6 feet high and 2 feet deep. There is a shelf of slatted wood that is about 2 feet deep and 7 feet long. Can I use the plastic shed for her to lay and the shelf for her to roost? Should I cover everything in straw? What is the most important thing I need to feed her? Should there be a little trough of water at all times?