It seems that you can install most modules from pycharm itself.

For me I have the professional edition, but anyways.

Try this if pycharm still says your missing Gym or other modules even after using pip installation:

-- In pycharm with your project or .py file open, go to 'File' then click on 'Settings'.

-- There should be a search box with teh magnifine glass. Type in 'Project Interpretor' and click on it.

-- The window will show all the modules already installed or implemented with the project you have open.

-- Don't see your module on there?  On the right of the list there is a '+' button. Click on it.

-- A window with all the modules that can be installed are shown as well as another search box.

-- You can use the search box and type in 'gym' or 'matplotlib' which I also didn't have.

-- Click on the package you want to install for the current project and click 'install'.

-- Once all the modules needed are installed your project should have no problem running your code.