In order to create a reverse DNS (matching an IP address with a domain name), start by going to the main page of your hosting interface (Manage / Servers), and click on the name of the concerned server :

This brings you to the administration page of this server.

In the "General Information" section of this page, use the "Reverse: [temporary reverse](Change)" function :

Simply enter the domain name you want to use as reverse DNS :

Click on change to finish.