From the description, and a look on the website - I think the fitting is similar the the Street Machine.....
On the Street Machine you need to remove the two bolts through the rear suspension and the carrier is then fixed in place with these. Underneath the frame is a "boss". The front of the rack then bolts using your single bolt to this.
So three point fixing
Cross piece of rack to boss underneath frame, two rear holes in rack fixed to suspension pivot. This piccie from the HP Velotechnik site shows what I mean
SMGT
Spirit
Edited....
You will need two allen keys to loosen off the pivot bolts, otherwise they will simply rotate, and secondly - be careful the "rear triangle" does not drop out. It is easy enough to replace, just a bugger aligning the washers, and plates with the bolt holes.