To be able to use the OmnextAPI, besides the Omnext API key (Where to find my API key), you also need the Portal Key in order to retrieve specific analysis data.
Login to portal.omnext.net using your Omnext credentials.
Navigate to the ‘My settings’ page using the menu on the left side of your screen.
Scroll down to the ‘Profile Information’ section. This section shows you to which Portals you have access, including their Portal Keys.