In a clean directory run:
git clone https://github.com/gbouvignies/chemex
Navigate to the chemex directory and run:
python setup.py install --user
To get the latest code using git:
git pull
Then simply re-run the install command above.
You should have installed on your system:
Newer versions of the above should be fine, as will be some older versions. However, Python 2.6 or earlier will not work. Please report any compatibility issues that you run into.