ignore what amazon said, just unzip the tar.gz zipped folder into downloads (or wherever you downloaded it to) and then enter the unzipped folder and copy the (exectutable) file "kindlegen" into /home/gregory/bin/
They want you to use a special kindlegen folder, but there's no good reason to.
I forgot that kindlegen came in a zipped folder.
It's been a little while since I downloaded it, I guess.