I beleive all the commands are well described in the helpfile.
If you really don't want to read the helpfile (altought I don't see why), you only need to know a few commands to get you started. First if you have any knowledge of DOS altogether, know that all the old basic commands such as cd and dir works in DOSBox.
First you will realise that you are on a strange disk labelled Z. That disk is emulated and is DOSBox default tree. It is not really important.
To get your game running you will need to "mount" the directory of your game into another drive emulated by DOSBox. For example I have my copy of Lemmings 2 - The Tribes on my real computer HD, located at c:\jeux\lemm2. To "mount" that game into DOSBox I would type (without the brackets) "mount c c:\jeux\lemm2" where c is the emulated drive I wish to "mount" the game folder to (could be anything from A to Y as long as I know) and c:\jeux\lemm2 is the directory where the game is located on my real HD.
After the game directory is successfully "mounted" on the emulated drive "C" (read above), you will need to move from drive "Z" to drive "C". To do this you use the old DOS commands. Simply type c: and you will get there. Once there you can use the DOS command DIR to look at all the files in that directory. If there is too much files and you can't see them all in a single screen, you can use DIR/W or DIR/P instead.
Once you are in the right directory (you should already be in the right directory if you did it well, but you might need to switch directory with the CD command) you only need to type the name of the starting file to get to the game. For example, I would need to type "L2-FIX.com" to play Lemmings 2. Note that you do not need to type the .com to do so, typing simply L2-FIX would be enough.
After you start your game use the CTRL-F11 and CTRL-F12 keys to slow or speed up the game as needed. You will need a big computer to emulate perfectly some of the new games and you should have no problems to run older games (like Lemmings 2) even with a slow computer. The perfect cycles (speed) for each game is very computer dependant and you should test a little with each game to get optimal speed.
Do not forget that you can go fullscreen with the ALT-Enter key.
I think that's pretty much it.
k: