Suppose you can start by installing it like :
$ pip install httplib2
you can try the same thing with easy install
too, or if you wanted to install in locally and not over the network then go to httplib2 github .
Clone/download it to your computer. Now go to the downloaded httplib2 folder location and run the setup.py
like this :
$ setup.py install
If on windows, make sure you have successfully installed python first and have set the environment variables path successfully.
This is a common command to install any module using pip or by locally downloading and looking for the foldert location>setup.py file and trying the second command mentioned above.