Here is the link to the manuals supplied directly from the authors of cPanel:

cPanel Manual
WHM Manual (for resellers and dedicated server owners)

Please Note all the functions in WHM may not be available for resellers, and some of the information contained in the WHM docs might not really pertain to dedicated server owners, for example, installation. This is of course handled ahead of time before you receive your server as the software has already been installed for you.

The docs are simply there for the features your paticular WHM has enabled so that you may have a look and see what cPanel has to say regarding the feautre you are seeking knowledge about.