You can access your Xoops installation via the server IP with without making any changes. You just type the URL below and change it to suit your account:

http://serveraddress/~username/path_to_Xoops_installation/

However, in order your links to access the content via the server's URL you should do the following changes:

1. You should change the following line in your Xoops mainfile.php. Here is the path to do this change:

define('XOOPS_URL', 'http://serveraddress/~username/path_to_Xoops_installation/');

You can edit it through cPanel --> File Manager --> find the file and click 'Edit' from the top box.