Publishing a website [on hold]

I'm doing a website for my church. They have a hosting service already with an out-dated website. The old website was made using dreamweaver (yuck). I hand coded the entire new website using html & css. I just don't know how the server side works. Where does stuff go? The hosting service makes you pay for documentation and technical support. I'm trying not to go that route. I think that the html & css files go into a folder called public_html, but how is a home page picked? Any light shed on this is greatly appreciated.