http://www.redrodgers.com/forums/showthread.php?t=4912
I got it from here. It is the beta version but as I mentioned it is very good. Simply download, extract to file, open the installer exe file and it will handle the rest. Some of the new weapons are tricky so I'd suggest reading the weapons manual, especially for the shipwreck anti ship missile on the Oscar.
Other then that your good to go. It will even work for those who use steam, which tends to complicate exterior mod installation
Please let me know if you have problems and let us know what you think of the improved RA