Thanks for that. I am sorry, I made a mistake. I was trying to get the "Jetpack Post Views" plugin working. That's the one that asked for the API key, but wont work.
I have now put in the regular Jetpack though and it seems to be OK. The reason I was trying to just put in Jetpack Post Views is because that was the only stats I really wanted and figured it would be a smaller plugin.
Should I just go with the regular Jetpack now and forget Jetpack Post Views or if I just want post viewing stats should I still try and get Jetpack Post Views running and then remove the regular Jetpack plugin?