[Coco] Accessing HD image under MESS

[arikboke at yahoo.com]

Folks,

This is a newby question.  I've just downloaded Mr. Withers ASM sources for
some of his Mark Data Adventures, including Black Sanctum, and I'm trying to
assemble them on MESS.  I've obtained an image of an 80meg HD (this might be
overkill) to hold the ASM sources and if need be, the EDTASM assembler. 
However, I do not know how to access the HD image under MESS.  I can "dir" a
floppy, but how can I "dir" an HD image? Or for that matter, how can I change
drive TO and FROM an HD image?  Would someone point me to a site that deals
with RSDOS commands?  I'm familiar with MSDOS but not RSDOS!  Come to think of
it, a site with an EDTASM primer might be helpful as well! :)  Thanks.

Sincerely,
David