I think in the installation we provide a Realfeelplugin.ini with a default configuration made by us (not sure now, but i think we do).
There were a Realfeelplugin.ini file available at rFC, but it disappeared when they decided to remove our mod from their site. Anyway that file is not that important, in the sense that it basically stores the personal settings for the FB set by the player. Some people like it stronger for some cars while others prefer a more gentle effect for these same cars. My suggestion is to experiment a bit with the FF settings (as explained in the manual you can modify them on the fly using keyboard shortcuts) until you're happy with it. In fact that the thing you should do everytime you load a car for first time on this mod :)