In your LocalSettings.php file, set $wgServer to the domain name of your wiki server, but leave off the URL path component. Set $wgScriptPath to the URL path of the wiki on the server. For example if the wiki is located at http://portal.example.com/wiki, then set these variables as follows:

$wgServer = "http://portal.example.com";
$wgScriptPath = "/wiki";