accounts created manually in shell, how to get into cPanel?

Hi - I inherited a VPS running CentOS 6.9 that had user accounts created manually in the shell, and also had Virtual Hosts configured in the shell. So, the accounts and Virtual Hosts do not show up in WHM / cPanel. In fact, the only way I can access WHM is by following the instructions here: interserver.net/tips/kb/access-cpanelwhm-without-password and, I had to create a new user account in order to use cPanel. How can I get these existing accounts and Virtual Hosts to be "seen" by WHM / cPanel?