Commando - secret rooms?

Sorry for asking a dumb question.  All these years of owning Commando on the 7800, I've never once gotten to the secret rooms I've heard about on it.  I've beat the game, I've seen the maps - to no avail.  

Can someone dumb it down for me a shade and give me in layman's terms how to get to these places?  

Thanks,

thursday83