Since you are restoring from a backup, you must use the same ost-config.php file you have backed up. Primary because that file more than likely will have Encrypt/Decrypt secret key that is randomly generated upon the initial installation, plus your database encrypted data would need that key.
After you have copied your backed up ost-config.php file, you only need to change the following lines:
#Mysql Login info
After these changes, and if the info properly matches your database information created in MySQL (using phpadmin) you should be able see your site online.
Let me know how that goes.