cannot mkdir permission denied

Hi. I am on a mac.
When I type ~$which git (returns) /usr/local/git/bin/git

In this tutorial, the following is typed: treehouse ~$ git init my_first_repository (returns) Initialized empty Git repository in /home/treehouse/my_first_repository/.git/

When I type ~$ git init my_first_repository (returns) fatal: cannot mkdir my_first_repository: Permission denied

I checked my permissions and I have all permissions set for the user me. drwxr-xr-x 10 root wheel 340 Sep 22 16:13 . drwxr-xr-x 9 root wheel 306 Sep 22 16:13 .. -rwxr-xr-x 1 root wheel 1603772 Jun 29 16:15 git -rwxr-xr-x 1 root wheel 14728 Jun 29 16:15 git-credential-osxkeychain -rwxr-xr-x 2 root wheel 162429 Jun 29 16:15 git-cvsserver lrwxr-xr-x 1 root wheel 3 Sep 22 16:13 git-receive-pack -> git -rwxr-xr-x 2 root wheel 793020 Jun 29 16:15 git-shell lrwxr-xr-x 1 root wheel 3 Sep 22 16:13 git-upload-archive -> git -rwxr-xr-x 2 root wheel 806404 Jun 29 16:15 git-upload-pack -rwxr-xr-x 1 root wheel 344042 Jun 29 16:15 gitk

I have tried this command from many directories but I am unable to execute the command.

Can someone tell me which directory I need to be to continue with the tutorial - and using git ?

thanks