The DNS management tool (in the sidebar) gives you various options to manage DNS records regarding your virtual machines or otherwise.
rDNS, DNS hosting, and dynamic DNS services are free. The latter two are service extensions that are currently in beta.
Set rDNS records
PTR records for the IP addresses assigned to your various virtual machines can be updated from the rDNS section. For each IP address, you can enter an updated hostname, hit enter or press Update, and then the PTR record data will be updated. Note that it may take several hours for the new DNS settings to propogate, as DNS servers cache records.
The hostname will be displayed whenever an PTR lookup is performed on your IP address, for example ping, mtr, and other tools perform this hostname conversion automatically.
lndynamic offers minimal DNS hosting, which can be controlled from the DNS hosting section of the DNS management tab. Start off by adding your domain by entering it into the Origin field. It will then appear in the zones table; you can select it there and manage DNS records for the zone.
The panel also lets you control dynamic DNS records, which are simply DNS records with a low TTL and which can be automatically adjusted from your computer via the lndynamic API (you must have API enabled for this to work). See the panel for more details.