Then under, "generic credentials", there will be a few accounts. The top one will prob be your email address (it is on mine anyway).
Click on the drop down arrow on the side and click "edit".
Change your info and don't forget to click "save".
TKS Gizmonster. I believe that I followed your instructions to the letter, replacing my old email address and P/W with the new + Save, but after shut down and start, nothing has changed on the start up screen.
I tried again and this time the address after going into generic credentials is
02rerggpqmml (+ its P/W)
which I don't recognise. I hesitate to changee that in case all goes to pot.
As long as your email address is okay at the sign in page, you'll be fine .... touch wood :)
That explanation in that link, looks a lot more complicated than it actually is. Just follow the explanation step by step and you should be fine .... touch wood ;)