Hi Dor,
The best place to go to for API documentation is https://developer.kaltura.com.
Under https://developer.kaltura.com/recipes, you'll find step by step code examples for various tasks, including adding metadata: https://developer.kaltura.com/recipes/metadata#/start
As for entitlement, you can set:
privileges = "disableentitlement";
and then pass privileges as the last parameter of the session.start() call. This will disable any entitlement enforcement.
As I said, channels are just categories with special attributes, look at the HTTP requests I posted above for examples.
If you have specific code snippets that do not work, feel free to post them.