First of all, change the value of your database host:
$mysqlhost = "localhost";
Second of all, unless you really placed your Mibew Messenger in the directory named Mibew and not in the directory named mibew, you should change the value of your Mibew root:
$mibewroot = "/mibew";
The case does matter.
Third of all, if you're sure that you have a database named db517763969 and a database user named dbo517763969 with the specified password that can create tables in the database and manipulate data in those tables, then you should point your browser to http://<your host>/mibew/install and let installer to do its work.