Creatign an A record for Domain Mapping

In the admin for domain mapping, it states the following:

If you want to redirect a domain you will need to add a DNS "A" record pointing at the IP address of this server: 109.109.237.90

How do I do this? I know about setting up a wildcard redirect adding * as the host & the adding the IP, but what do I add for the host in the section above fr domain mapping?