Online Documentation: 
WHM™ Documentation cPanel® Documentation
PDF Documentation
Right-click and select
Save Link As to save these files to disk.
WHM Documentation (PDF) cPanel Documentation (PDF)
If you have any specific questions that may not be addressed clearly in the above documents, then feel free to ask here.
Just a note: Cpanel and WHM is widely known as the best control panel software for hosting and managing your site. If you have any questions it is most likely already been answered on the net. Try searching google with the question or problem you are having making sure you include the words cpanel or whm in the search. If you have no luck, then we are more then happy to answer any questions you may have with using your new control panel.
Thanks, Buy-host Support Staff.