As long as Sitemason is hosting DNS for your website (which is the most common setup) and your domain's Name Servers are pointed to:
Your site's DNS is managed via the DNS tab within the Site Settings panel. If you aren't familiar with DNS or how to manage the various records, it's best to leave this section to your IT professional or web developer.
The DNS Manager allows for management of seven different records types:
The WWW record controls where www.example.com points to, and if your site is a Sitemason website, it should be set to web.sitemasonhost.com. The Domain Record, listed right beneath it, is the apex record. The apex record controls what happens when a visitor types "http://example.com" (leaving out the "www"). This should always point to 220.127.116.11.
MX Records are used to point to your email service provider. For example, if using Rackspace for email, they might be:
Or perhaps using Gmail, something like:
In both cases, the number preceding the record is the Priority, and declares what should be tried first, second, etc, in case the top priority servers fail.
A, CNAME, and AAAA
A, CNAME, and AAAA Records are used to map a hostname to an IP address or another hostname. For example, a common A Record might look like:
CNAMEs then map hostnames to other hostnames like:
AAAA Records serve the same purpose as A Records, but accept more complex IPv6 addresses like:
Finally, TXT Records are employed for a number of uses, but most common are SPF Records and Google Domain Ownership Verification.
Here's an example of a Rackspace SPF Record:
v=spf1 include:emailsrvr.com ip4:18.104.22.168 ~all
And a Google Domain Ownership Verification:
A full help article on DNS and using the Manager can be found here.