I think that you need to go back to square one.
Did you try easy_install oauth2?
Did you try pip install oauth2?
If neither of those work, then you need to install it manually. Having read through the readme on github you know that oauth2 depends on httplib2 so start by installing and testing httplib2. Don't go any further until you know that httplib2 is installed and functioning correctly.
Next step is to manually install oauth2. Lots of Python modules have a setup.py script so you can just change to their directory and run python setup.py install to get the module properly installed. In fact, oauth2 does have such a module so you should try that first.
Then if it still doesn't work it is a matter of making sure that the oauth2 directory is on your search path. Most people would put it in their site-packages directory, but it is OK to just add the oath2 directory (the one containing __init__.py, to the Python path. That is what .pth files do.
If you don't have easy_install or pip, the easiest way to solve this problem is to download http://python-distribute.org/distribute_setup.py and execute it on your system. This will install both pip and easy_install for you.
