Step by Step installation for OS X

i) If you do not already have an application for dealing with gzipped files, then install OpenUp from here.
ii) Download the disk image from the download section
iii) If your web browser doesn't automatically open it, double click on the file you just downloaded in the Finder. You should see a new Finder window with one file in it, a disk image (xmd-0.1.dmg)
iv) Double click on the .dmg file to mount it. You should see a volume called Xmd appear and the Finder should open a new window with 4 items in it.
v) Drag the Xmd icon to your Applications folder (you can't miss it, it's the one who's icon is a picture of a Sony MZ-N1)
vi) Enjoy.