I have both python2.7
and python3.2
installed in Ubuntu 12.04
.
The symbolic link python
links to python2.7
Firstly, you need to install pip for the Python 3 installation that you want. Then you run that pip to install packages for that Python version.
Since you have both pip and python 3 in /usr/bin, I assume they are both installed with a package manager of some sort. That package manager should also have a Python 3 pip. That's the one you should install.
Felix' recommendation of virtualenv is a good one. If you are only testing, or you are doing development, then you shouldn't install the package in the system python. Using virtualenv, or even building your own Pythons for development, is better in those cases.
But if you actually do want to install this package in the system python, installing pip for Python 3 is the way to go.