Hello,
I believe you've logged into KMC using the Admin Console credentials you've set during the installation, this will not work.
Instead, please login to Admin Console - $YOUR_HOST/admin_console, create a new partner under Publishers->Add New Publisher and log in with that. You can also automatically login to your partner's KMC from Admin Console once you created the partner, by going to the Publishers tab and, in the table row for your partner, clicking on the "Actions" select box, selecting the "Manage" option.