If you look at "Domains" in your web panel, you should have the option to add/transfer a domain.
DH gives you several options (park, redirect, mirror), all of which are free.
It sounds like you registered the address somewhere else, which might change the math on this one (I think DH free parking is for domains registered through them). You should send a question to support for "official" answer on what they'll let you get away with. They might have some advice on how to transfer EVERYTHING, so you eventually have one-stop shopping here for all your domains and web services.