I have only embroidered on ribbon a few times, but it was pretty easy. I hooped my stabilizer (I think I used water soluble, but you could also use a sticky back tear away). Then pin the ribbon to the top of the stabilizer with your design area centered. My machine has a little feature to check sort of trace around the the area that will be sewn, so I run that just to make sure it is centered. Then put the presser foot down and go.
I also belong to SewForum and this tutorial shows how another person embroidered on ribbon. http://www.sewforum.com/viewtopic.php?t=55904