There is a menu.ini guide on Plissken's FTP site, under that screen name "Scudder". It's a good place to start.
There are also 2 good tutorials on SubSim, here
http://www.subsim.com/radioroom/showthread.php?t=111832 and here
http://www.subsim.com/radioroom/show...8.ini&langid=5. The first one is on an SH4 thread, but the file layout is exactly the same, so it all applies. These should help you get started.