Hi there, could anybody tell me where do I have to go when I found that prison key? I have no clue I walked back outside but there are no doors where I can use the key. Also when I get back into the church die only way I can go is down the stairs where all these cages are.

Please help

This is where you should be.

This is from a walkthrough (this one specifically but obviously don't click it if you'd rather go through the remainder of things on your own):

"Head back into the prison area and grab a battery from the back of the cage area. Now crawl between the cages on the left side of the area to find a door. Use the key on the door to unlock it and move into the next room."