What instructions are you following?!?!
The Wiki page has two sets, one for people new to DreamHost and another for those that are already DreamHost customers. And it's the set of instructions for existing customers that requests the account number.
People new to DreamHost would get an e-mail message (because they provided an email address and wrote it on their fax, too)
Here's a tip: always check the "discussion" page for a Wiki article, you'll see that for this process its suggested you can either choose pay by check or pay in advance and get re-imbursed depending on time constraints.
Customer since 2000 openvein.org