Briefly, your cPanel will have a Reseller_setup package, by default. The limits are 1MB disk space and 1MB bandwidth – not enough to do anything! You can find out about adding more space to your account here.
Before you can create packages for clients, you must create one for yourself. Once this is done, then you may go to “Upgrade / Downgrade account” and assign that package to your control panel.
You may then use the same process to add client accounts to your WHM. For additional information, this video tutorial will walk you through the process: https://www.hostpapa.com/knowledgebase/tutorials/tutorials-whm.shtml
Need more help? Please open a support ticket here: https://hostpapa.com/dashboard
Support ticket tips/info: https://www.hostpapa.com/knowledgebase/kb/how-to-open-and-access-support-tickets/