The white screen means that you have a critical error that is halting execution, but you do not have PHP messaging turned on to tell you what that error is.
Turn on debug mode in WordPress so the error message is displayed. Otherwise you don’t have enough information to correct your problem. Set the WP_DEBUG constant in your wp-config.php file to true. See: Debugging in WordPress
Once you know what that error is, you can edit your question with more information.