Adding an outside domain to hosting?


I have a shared server hosting plan and a domain with dreamhost. Recently my mum asked me if she could host her web page on my hosting plan. As the FAQ says it’s okay to have multiple domains I figured it would be fine. The problem is that I’m a total newbie and I have no idea how to connect my hosting plan to the domain name she owns - I looked on the wiki but it said their method couldn’t be done if the domain name wasn’t a .com/.net etc. It’s a, so I guess that’s out, but I’m not sure how to proceed.

Can anyone give me any tips? Sorry for the kind of stupid question! Thanks very much :slight_smile: