Actually, I was told that little bit of information several years ago. Also, you can generally locate the G-spot as being at or slight beyond the clit. On the inside, of course. And usually a little to her left. Which, interestingly, corresponds with the above description.
I can't get to anything but that blurb. Am I doing something wrong? I logged on but all I get is that little bit and the big banner "LEARN MORE".
Click on the Skip button underneath the Learn More banner, then click on Download Now. You'll need to be logged into Facebook. It will download a PDF file. The chapter you get doesn't actually explain the 15 minute part, its probably not stuff you haven't read before.