Help documentation and a user guide for the KFHD is here.
BTW, there are several third party user guides now available for the Kindle Fire HD. I've read a couple. Nothing very surprising if you are already familiar with the first generation KF and in some cases sloppy editing of what is obviously a revised version of an earlier guide leads to errors, e.g. discussion of the illuminated power button that doesn't exist on the KFHD.