So if its like my TV you’ll have a ‘home’ button on remote control. From there you should be able to access a store or something similar. Then you can search for discovery. Good luck!
It’s not quite as simple as just subscribing, you need a platform to watch it on. I don’t think you can just add it to your normal TV channels.
If you have Sky or Virgin TV then you can just do it through them easy enough.
If not, then you need a Smart TV where you can add apps like Netflix...