Can't login! Please help!

I only get a white screen with no login! I tried on Chrome and Explorer. I was trying to change the style of my search bar and entered code into the CSS (maybe in theme php or the main CSS?)and clicked “update”. When I tried to “view page”, it only showed a white screen and won’t let me login. I don’t know where to find FTP and I downloaded PHPMyAdmin but don’t know how or where to install it.
Please help:
http://www.earthfairlacrosse.org/wp-admin

Thank you in advance!