adding new ssh user with access to opt/git directory

Hi guys, i've install the git addon for my readynas duo and I would like to setup gitolite http://sitaramc.github.com/gitolite/index.html#qi

The git addon sets up a directory in /opt/git

I've setup a new git user in frontview but how to I give them ssh access to the /opt/git directory? Also will this new user have access to the git commands or does something need adding to the path?

Is it also possible to add the /opt/git directory as a share so I can see it in finder?

Many thanks