First of all, if at all possible get to a current version of calibre (unless of course you are constrained to using 1.48 because you have XP).
Then, within calibre DO install the "Kobo Utilities" plugin.
Finally, please DO read
Kobo_Shelves_and_Collections on the Wiki (or the older version of it
Quick Guide to Shelf Management with calibre 0.9.1 & above (Touch / Glo / Mini /Aura) in the forums).