To be honest that is the one part of the noob tutorial I don't agree with for beginning users its much easier to point them to the way to set directories and create the ini through the UI to do so just open MAME with no game loaded then go to Configure options
from there you can set your directories by choosing directories then when you back out of that menu you just choose save configuration and you should be good to go after that.
to change directories in the command line though you just type cd (for change directory) then add the next part of the directory until you get to your final target directory