Frontend Operations can take place in easy or complex Scenarios. In any Case, you must have a valid Frontend Session:
If you only want to enable simple User Interactions like Rating or Comments, start with Media Interactions:
If you are using the nexxOMNIA User Model too, you will need the User Endpoint for Profile Management and User defined Content:
And in the most complex Cases, you will also use the nexxOMNIA Payment APIs. You will find the Details of them here: