Cannot Install Theme ( White Page )

I have tried multiple methods as listed on the support threads within this support site. I tried doing it through FTP as well as through the back-end wp-admin. However at first I was getting the “Are you sure you want to do this? Please try again” error. When I tried FTP I finally got it installed, but when I clicked to apply the theme everything went white. When I went to my website URL it went white and would display nothing and I could no longer access my Wp-Admin either. I renamed my folder in order to “break” it and restore the default theme. Now I am even trying to use the live preview for the theme, and everything is blank again.