The location of the python.exe for Python 3.3 can vary depending on how you installed it. Probably the best bet is to search w/ Spotlight for python.exe, press "Show All" in the drop down menu, change to "File Name" instead of "Contents" search and then click on results to see the full path at the bottom of the search results window. You'll get at least 2-3 results and the full path should make clear which is the correct one. Then enter that into Python Executable in the Configure Python dialog, accessed from the Source menu in Wing 101. You'll need to restart the Python Shell in Wing 101 from its Options menu before it switches to the new Python version.