In the portal of the PowerBIConnector.nl you do the configuration of the Power BI connection with Exact Online. You can reach this portal on https://portal.powerbiconnector.nl.
As an administrator you can configure here which users have access to which companies. As a user you make the connection with Exact Online here and you can generate the Connector Key that is used in Power BI.
By the activation of your account on PowerBIConnector.nl you have received an activationmail. In this mail is your username with the steps to activate your account. The first user is automatically the administrator of the account.