setup docs unhelpful

The following text from the project's README.rst file needs more detail imo:

And enable it from somewhere in your ``$PYTHONPATH``::

   [extensions]
   hggit =

I found another site (https://hg-git.github.io/) that seems to be saying this should be put in ~/.hgrc? Or maybe that is old info and I need to create a file with any name in my PYTHONPATH? Either way, I'm going to have to do some guessing, and a little additional info here could prevent that.

Also, the https://hg-git.github.io/ site suggested that maybe the text that goes in whatever file should be holding these settings should actually be this:

[extensions]
hgext.bookmarks =
hggit = [path-to]/hg-git/hggit

Which is correct or better, or can we have some text here describing why you might choose one over the other?