If you go to my.gameservers.com and login to your members area you should see a list of your subscriptions. If you click on the "Mods" tab which is located across from your server information you can view/install some mods we have available.
If you wish to install mods to your server you can do this as well through the servers FTP. If you are unfamiliar with ftp, please check out this thread in our forums about ftp:viewtopic.php?t=76
For your game server, your ftp login information is located in your members area by clicking info next to your subscription.
If you wish for us to install a mod to your server we can do that as well, just please provide us a valid link to the mod you wish to have installed in a support ticket that you have submitted from your members area.
We have 24/7 support here to assist you anytime you are having an issue with the server, in your members area at my.gameservers.com if you click the "Support" tab you can submit a ticket.