Follow the below steps to create account in your reseller/whm panel:

1.  Login to whm panel
2.  Click ADD NEW PACKAGE >> here enter the details like plan name, disk space, bandwidth.,,, and click CREATE
3.   Click CREATE NEW ACCOUNT >> enter the domain name, user name and password and at the below choose the package name and click CREATE
4.  Then update the name servers given for your hosting account in the domain control panel

Your customers can add, delete, or modify accounts and customize some settings for their hosting account at the URL

http://yourip/cpanel/ or http://customerdomain.com:/cpanel/

and the login details are

Control Panel Username :  as you gave while creating hosting account
Control Panel Password :  as you gave while creating hosting account

Your customer should Upload the web files into the “public_html” directory.