I'm not sure which installation guide you're referring to, so here's the best advice that my little old brain can give -
1) The DOS folder you are talking about it one that you are supposed to create yourself to hold your games etc. therefore you won't find it unless you create it.
2) Take a look at
this really simplified explanaition of how to run games in DOSbox.
There are a few links to DOSbox guides on this site, if you can let me know which one you found confusing I could probably be more help. But, if all else fails - use VDSMsound! It's simple, and requires no fiddling around in a psudeo DOS-screen (that's just my personal preference anyways
)
EDIT Take a look at
this help topic, it should answer your question. Good luck
