All the steps are mentioned in here, but for your convenience, here goes it inline:
Installing prerequisites
Install latest pip distribution: download get-pip.py [bootstrap.pypa.io] and run it using the python interpreter.
Installing PySide on a Windows System
To install PySide on Windows you can choose from the following options:
Use pip [pypi.python.org] to install the wheel binary packages by issuing the command:
pip install -U PySide
Use setuptools [pypi.python.org] to install the egg binary packages by issuing the command (deprecated):
easy_install -U PySide
Download and install the packages from the PyPI page [pypi.python.org]
Provided binaries are without any other external dependencies. All required Qt libraries, development tools and examples are included.
Then, you can grab the Qt 4.8.6 version from here:
http://qt-project.org/downloads
Please note that there is no installer for VS2012 off-hand, so you should use an older version or mingw. Alternatively, you could also build Qt 4 yourself.