Both rule files should be located in your main installation folder on your computer:
C:\Westwood\RA2\
C:\Program Files\EA Games\Command & Conquer The First Decade\Command & Conquer Red Alert(tm) II\RA2
However if you’re using the CNCnet client replaces rules.ini with spawner.xdp. Nevertheless that shouldn’t be an issue as you can edit it in the same way.