How do I connect my iPhone to my Apple TV box?

The Apple Remote app doesn’t work anymore, because the remote is now on the Control Centre.

But when I try to link the control Centre remote to the Apple TV box, I just get an endless « Searching for TV ». What am I doing wrong?

And our separate Apple Remote (handheld) has stopped working. I plugged it in to charge it, but still doesn’t work.

Any thoughts?