Problems saving changes to /etc/sshd_config

Question

I am trying to setup my mac mini as a secure git server, I'm following this very helpful blog post, http://www.tomdalling.com/blog/software-processes/how-to-set-up-a-secure-git-server-at-home-osx.

Now I get stuck at number 6 when i am trying to save changes I have made to the /etc/sshd_config file. I am logged in as my administrator account and can open the file correctly, when I try to save it I receive the following error:

The document “sshd_config” could not be saved. You don’t have permission.

To view or change permissions, select the item in the Finder and choose File > Get Info.

I have tried to change the permissions using chmod but I can't do this either. I also can't locate it using the finder to be able to change permissions using File > Get Info as suggested in the error message.

Does anyone have any idea how I can resolve this? Please help!