You don't have to add them manually, just copy them in this format.
ip: port:user: pass
Click on the "Manage" button in the Select Harvester & Proxies Section and then click on "Load Proxies" and "Load from Clipboard" option.
If your proxy provider didn't provide you with user n pass, then you don't have to use it. Maybe you have to whitelist your VPS IP from the proxies panel in order to use them.