Can only play add-on TNT sport, via Discovery+, on phone

[GrandmaJo]

Non tech savvy granny here.  I've had the inclusive 'extra' of TNT sport via (included) free Discovery+, for some time.  However, I've only ever been able to watch programs on my phone.  I've never been able to activate it on my tv or all-in-one pc.  Whenever I try, I'm told at various points that I need to subscribe to Discovery+ and/or TNT sport which, of course, is included in my phone subscription.

Is it a case that once I've initiated TNT sport on my phone, I'll never be able to play it on another piece of equipment?  Or is there an easy solution?  Not much fun watching footie on a phone!  

[Chris_B]

@GrandmaJo   You can only watch on the device in question as that’s where the subscription is for,   But you can cast from your device to a google chromecast  or Apple TV.   

[GrandmaJo]

Many thanks Chris_B, for your reply.  As I said, non-tech savvy so no idea what 'casting' means, but I'll do some on-line surfing and hope to find an idiots guide that will hold my hand through the process!  Fingers crossed.