Changed Site URL

I had my site running yesterday afternoon but I wanted my homepage to my homepage not my blog so I screwed around with the site url (Bad idea) and now I can’t access my wp-admin … and my formatting is completely gone!

I’ve tried looking into the files and the wp-admin.php but html was never my strong suit and I have no idea what to do to fix it and just reverse what I did…

PLEASE HELP.

I’ve read forums and tried their advice but it hasn’t done anything so… help ??