Hi there,
I was reading the documentation in regard to that, but after conferring with some colleagues, you should be able to use the buy now option as well.
I just ran through the steps using the "buy now" option, and I was able to see the "email" tab next to the "website" tab. What browser are you running?
If you could, would you make a screenshot of what you see on screen when you get to that step?
Here's a bit more information about how to take a screenshot:
http://en.support.wordpress.com/make-a-screenshot/
You can upload the screenshot to your media library and I can view it there.
Cheers!