Reverse DNS works exactly as you would expect. Instead of a DNS query on a domain that returns an IP address, when you have reverse DNS configured correctly, a reverse DNS query on an IP address returns your domain. While not many services require you to set reverse DNS, one service that does is mail. Without a reverse DNS record, your mail could endlessly be sent to spam boxes.

To set your reverse DNS record, navigate to the VPS control panel and login. On the left navigation menu, you will see a menu item "Reverse DNS", navigate to this page. Once you are on the Reverse DNS configuration page, you will be able to select the IP address of your server and your domain.