Your main server tasks, such as creating accounts, packages and monitoring server resource usage are performed in WHM whilst the end user tasks such as creating mailboxes, databases and managing files are performed in cPanel. You can auto-login to any cPanel account that you create in WHM by clicking the cPanel icon within the “List Accounts” section of WHM.
You will find detailed instructions of how to use WHM and cPanel in our support database and the following online documentation provided by cPanel themselves:
WHM: http://docs.cpanel.net/twiki/bin/view/AllDocumentation/WHMDocs/WebHome
cPanel: http://docs.cpanel.net/twiki/bin/view/AllDocumentation/CpanelDocs/WebHome