In your PyCharm project, go to File > Settings > Project > Project Interpreter. If you used virtualenvwrapper or PyCharm to create the env, then it should show up in the menu. If not, click the gear, choose Add Local, and locate the Python binary in the env. PyCharm will display all the packages in the selected env.
Tkinter is installed by default. If python or Tkinter is not installed, install Python 2.7 from http://www.python.org. Tkinter is installed by default. Test by typing python at the terminal and then import Tkinter.