Click on a Primary Domain or a Dynamic Domain to edit it. Generic site setup might look something like this:
yourdomain.com A 127.0.0.1 www.yourdomain.com CNAME yourdomain.com
You'll want to use a more interesting IP than the 127.0.0.1 loopback address, of course.
If you have a mail server, telnet to port 25 of the server and notice the hostname after the 220. Perhaps you see something like "220 mail.big-isp.net ESMTP Mail Server". Double-check that "telnet mail.big-isp.net smtp" gives you the same result, then add
yourdomain.com MX 1 mail.big-isp.net
to your domain records. Ten minutes later, send a test email to <yourself@yourdomain.com> to make sure that you can receive mail successfully, and also ask http://DnsReport.com to verify there are no red flags on your domain setup.