You'll need to use a piece of software called an "FTP Client" (such as Filezilla) to connect to the FTP Server on your webhost.
If you cannot understand that statement without having to Google it, I highly advise against you transversing within the files on your webserver as you can destroy the inner workings of your site and suggest you instead hire out to make changes to any coding.
In either case you (or someone else) needs to login to your server via FTP and change an integer in the libs/mysql.inc.php file so that errors are displaying to the browser.
