Yes, an email address can now only be associated with 1 nickname - so your bidder and administrator nickname and password will be the same. If you already have an administrative account you automatically now have a bidder account. You just need to add a credit card to your account.
If you already have a bidder account and are invited to be an administrator for an auction the system will prompt you to log in with your bidder username and password.
Once logged in, you can use Auction Manager, Marketplace or browse/bid on auctions.
If you don't remember your password, click on the Forgot Password link on BiddingforGood.com or in the Auction Manager log in page.