When you say "system Update" are you referring to the DSi-XL or the EZ-Flash Vi card?
The DSi-XL firmware update is done through wifi and Nintendo's web site. It is actually an option under the "Settings" menu.
For the EZ-Flash Vi - just google it and you should find directions on getting the update and how to apply it. You do need a DS or DS-Lite to apply the update to the card.