It sounds like you are referring to the six digit code that appears on your television screen.
This is not the 3 month voucher code that came with your new stick, where the code is used to initially activate the stick.
Try following Step 5 of this help guide.
And use this link below with a PC or Mobile internet browser to use the code that you see on your television screen.
You are not the only one turning into his parents because I found the same thing happening to me and, I now realise, my poor old brain can't learn any more new stuff.
Nevertheless, I am still discovering, for me, unknown facilities that my current software and apps have and that, I have found, is an adventure in itself.
We sent our grandchildren a postcard from Iceland.
On it, I thought I had better explain that this is what people did before they had WhatsApp, and still do if they can’t work that
I used to dread turning into my parents in later life, but of course you never do; some of you always was them, and that, with what you bring to it yourself, is what your kids in turn dread turning into.
But seeing all the eider ducks in Iceland made us nostalgic for going to bed as children in the old pre-duvet days, as celebrated by Philip Larkin in his poem about family life, starting:-
“They tuck you up, your Mum and Dad...”
If I am remembering it correctly, that is.