Wil,

Here's the direct link:
http://www.lowrance.com/software/Upgrades/AirMap/airmap_100_190.asp

Here's the long way there:
1. Go to www.lowrance.com [lowrance.com]
2. At the bar near the top, put your cursor on "Products" then select "Software" from the drop-down menu.
3. Sroll down to near the bottom of the screen and select "Software Updates".
4. Select the update for your model.


[Linked Image from visitedstatesmap.com]