Are you wondering about installing two different version of python ? in this case is 3.x and 2.x. You will have no problem if you use linux as development platform as your distribution will arrange it for you, but I was afraid this is not the case with windows. So how is it going with windows?
TL;DR You don’t have to worry, just download and install python 3 package in your windows machine
Python developer realize this will be a problem for us, so they write specification to handle it. You can read the specification here (PEP 397), I quoted the abstract.
This PEP describes a Python launcher for the Windows platform. A Python launcher is a single executable which uses a number of heuristics to locate a Python executable and launch it with a specified command line.
Now just download python 3 package from python website and then install it, make sure you check the option to add it to system path. From now you still can use your python 2.x and start to develop application with python 3.
Use python to run python 2.x
Use python3 to run python 3.x