go to the battery hen welfare trust web site www.bhwt.co.uk
i have been keeping hens for yrs now, i have 21 in total plus 2 ducks and they are wonderful!
I have also rescued hens, along with other animals, so have some experience in this area. Its very rewarding, but also heart breaking as you cant even begin to imagine the awful life they had lead prior to you taking them home, they are in a right state!! I can promise you, that you will never eat any non free range products again, or broiler birds!!
They will need to be kept in the shed for a cpl of days without access to outside, just to get them used to the extra room, then open up the shed and let them decide what to do, they may go racing out, they may take days, but let them judge it, never force them x
They will come vaccinated, but still keep a look out for any signs of disease/infestation, or illness as they really do come in a sorry state.
Feed them a mix of corn and layers pellets, along with a tray of grit to help grind down the feed in their crop, make sure you buy a good quality one with oyster shell in it.
The feathers will grow back and they will begin to trust you, it will just all take time, alot of love and care on your part too.
If you dont feel like you can commit to caring for rescue hens then dont do it, you can buy pullets from many different places, look on google and suppliers will come up in your area.
With regards to your shed, make sure its weather tight and doesnt have holes where the wind can get through, give them nesting boxes, one box to 3 birds, and perches, not too far off the ground as they wont be used to them, use straw, not hay as it can harbour mould which will cause respiritory problems.
Just ask if you have any more questions, i will kepp an eye on this post and hopefully i can help answer any more questions x good luck and happy chookie keeping xx