You need to copy the share/bochs/bochsrc file to your home
directory and name it .bochsrc.  Then edit it to your 
tastes defining the hard drives, and floppies as needed.

Documentation is available on the website, and a copy of that
website is in share/doc/bochs/.  The file install.html will
assist you in creating a HD "file". (A raw disk partition can
be used as well)