1) Setup python 2.x - Python 3 is not supported.
2) Download s3cmd from www.s3tools.org
3) Add python directory to your global path (should be C:\python2x)
4) Run python setup.py install
5) Run python s3cmd --configure (from the build path)
You can edit the values in the setup configuration at
c:\Users\"username"\AppData\Roaming\ in a file called s3cmd.ini
I'm using s3 with Greenqloud and if you download a the tarball from them you can replace the contents s3cmd.ini with _s3cfg from Greenqloud.
Then you can run commands
python s3cmd ls
Comment below if you run into trouble, I could try to help.