Quote: "Or is there a folder for FPSC? "
Yes. You cannot add media from in the game, you can only select what is already in the folder. If you did a default install (English version) then the folder in located at C:\Program Files\The Game Creators\FPS Creator\Files. In the Files folder you will find folders for audio, entities, scripts, segments, etc. This is where you add the content, to it's respective folder.
If the content does not have an installer, follow the included direction on where to place the files, or contact the creator for instructions. Otherwise, place the contents of the entitybank folder in the entitybank folder, and so on.
Best.