At least read the first post of the thread
Fall of the Rising Sun Ultimate - Full Release, but better still would be to read some of the pdf that are linked to in the Support folder of the mod with "01_FotRSU_TableOfContents.pdf", which can also be started from the "01_FotRSU_Support_TOC.bat" file, which will be in the game's folder after mod activation... Everything you should know is in there...