Hablo mucho inglés, pero es dificil a me entiendes a veces.
1) Create a User who will own your domain. You may have already done this.
2) Use the Control Panel->Manage Domains to Add a New Domain. Fully Host your real domain name that you'll eventually transfer over here.
3) Populate your domain via FTP, or whatever. You can FTP to machinename.dreamhost.com (the machine name is listed when you Manage your User).
4) Use the Control Panel->Manage Domains to Mirror your existing domain. Call it yourdomain.dreamhosters.com
Be careful when populating your domain by making sure that any references to your fully qualified domain say 'yourdomain.dreamhosters.com' and not 'www.yourdomain.com'.
Tienes más preguntas?
-Scott