Fade In Professional Screenwriting Software is compatible with many third-party dictionaries, including French, Italian, Spanish, German, Russian, and many, many more. Links to these can be found on the Download page at http://www.fadeinpro.com. Click on Extras.
To install additional language dictionaries for Fade In Professional Screenwriting Software, download the appropriate file(s) from one of the listed sites. You may need to extract/unzip the package: what you want are both .dic and .aff files for any given language.
From an open document in the application, select Document > Check Spelling, and from the language choice drop-down, selected Install/remove.
Click the Install button, and select the dictionary (.dic) file that you want to install. (Repeat for multiple languages, if desired.)
Note that some dictionaries are distributed in the .oxt Open Office Extension format. In order to open these, just rename to .zip, and open as you would a zip archive to find the .dic and .aff dictionary files.