Someone sent me here :)
It turns out I've written a guide on the same subject... unfortunately.
But fortunately it turned out to be more in depth, with configuration of all accounts and use of boinctui. I've repeated the whole registration process starting with fresh google email, with screenshots step by step and good explanations along the way.

If you don't understand something, have problems get in touch here
Free Gridcoin From Google - In-Depth For Dummies