First download the 2 rar files from luthiers beta 2 Thread. Then unpack the files into your main CoD directory. Overwrite the old files with the new ones. Don't forget to unpack the il2 15866 Corepatch rar File. Otherwise the game crashes evertyime an explosion takes place.
Then delete all files in your CoD cache (Documents/1C Soft Club/ Il2 Cliffs of Dover/ cache) except the shaders folder but delete the CONTENT of the shaders folder as well.
After that you are ready to go. If you want to revert to the Steam version, rightclick on CoD in Steam. Go Properties and let Steam recover the standard files to get the pre-beta version.
edit: oops got to learn to write faster