If your device is new enough, you may be eligible for TomTom's latest map guarantee that gives you one free map update within 30 days of the purchase of a new TomTom device. Our XL 340 S Live was outside of the window of opportunity.
Click the Add Maps button and you'll be taken to this list of available map updates for your particular unit. Users can update their current maps or add new areas, for example European map data for an intercontinental vacation.
With your map chosen, you'll be prompted for a method of payment, after which your maps will be available for downloading and installation. A full map update can take as long as an hour to download and be flashed to your GPS device. You shouldn't unplug your GPS device during this time, so be sure to allot plenty of time.
With your new maps installed, head back to TomTom Home's main menu and select "Update my device" to check for other updates, including fuel price data, TomTom Map Share corrections, and software updates.