You need a Club ID and PIN to get in the first time. Once in, you set up your login name and password (or just link to it if you have already registered on a Disney website.) If you didn't get your Club ID and PIN with your paperwork, then call Member Services and they can give you that info over the phone.
You cannot make reservations online. What they call booking online is really using the website to send your reservation request to MS via email. Turnaround time is about 3 days. It's better to call.
You can usually bank online but they do disable this feature from time to time. The members' website (or rather, the database and the software behind it) isn't as stable and reliable as it should be.