In Sonarr go to: Settings -> Indexers and click the large + icon to add a new indexer. Then click Presets under Newznab and select NZBFinder.ws.
Make sure everything looks like this but enter your own API key:
Please note: You can add other TV categories here as well. For example to add sports just add 5060 to the Categories field. You can leave 5010 out as that is WEB-DL, we’re not using a specific category for that YET. It ends up in the SD or HD categories mostly for now.
5045 is TV > UDH (4K) which at the moment of writing does not contain releases yet. But it’s added here to future proof your setup.
Click Save and you’re all set!
If you have an elite account you can add Spotweb too. Add a new Newznab indexer and use Custom. Make sure it looks like this (enter your own API key) and click save: