If you want to add new users to your ProxMox servers so they can add new VMs, and administer it, this is a very simple process.
First step is to add the user and set their password:
pveum useradd bob@pve -comment 'Bobs test user' pveum passwd bob@pve
Then you need to give them permissions as admin
pveum aclmod / -user bob@pve -role Administrator
Now just make sure you pick ProxMox authentication when logging into website.