After downloading and unzipping, I copied the .pyt file and the Doc folder to my
C:\Users\<username>\AppData\Roaming\ESRI\Desktop10.3\ArcToolbox\My Toolboxes
folder (replace 10.3 with your version, if needed). I then restarted ArcCatalog and it appears in My Toolboxes
Although I copied the Doc folder there....I think having it in a handier location would be good since it contains two PDF docs....(so I'm moving mine someplace else).
EDIT: by the way, I noticed that 10.3.1 is required for some of the tools, so keep that in mind.