I believe it's outlined in the Aria manual, which, I also believe is available on this web site here:
Oops, so it's not...even though the Aria is the poster camera for the Manuals section ;-)
Two things. There is a switch on the inside, next to the pressure plate, that allows the data imprinting on the first 2 or 3 frames, depending on how many frames your film is. It's really cool, turn it on.
Second is, you use the buttons on the back (flip down the control cover) to set the time/date, and select the impringing mode. Dashes "-----" means no inter-frame imprinting. Anything else is what will get printed.
So, set the date/time, select the imprinting format you like, turn the switch inside the back next to the pressure plate "on", and run a roll of film!
Thanks for the helpful posts! I just got the databack the other day and find I have to order batteries, so will be a week or so before I can actually turn it on and see how it works.
May have more questions then.