The CAS is maintained by LSAC and can be accessed through their website, www.lsac.org
You will need to register for both an LSAC account (free) and a CAS account (not free). You will need to register for an LSAC account in order to register for the LSAT and you can do that at any time. You should register for the CAS roughly six weeks before you plan on submitting your applications. That will give you plenty of time to get everything assembled and submitted.
Yes, there is. In fact, the LSAC does a fairly good job of supporting users and guiding you through the steps that are necessary to take. For example, you can start here for links to frequently asked questions. There are also video tutorials that are very useful. Those can be found here
In addition to these resources, LSAC offers support through phone and e-mail contact. That information is available here