Make sure that the books you purchased from Kobo that you want on your new device are in "I'm Reading". You can move them there by bookmarking them in the purchased section. I don't know what version of the desktop you are running, if the older one, you should be offered the new desktop when you choose something like "update your library". If not, you can download the new desktop from Kobo.
After that, it is just a matter of attaching your Kobo (I am assuming, if 12 months old it is Kobo 1) and choosing sync to get the purchased books onto the reader.
The Kobo 1 user guide can be accessed from the pick menu here:
http://kobobooks.com/wifi_support . It has both the WiFi guides and the Kobo 1 guides.