UPDATED LOWRANCE INSTRUCTION HERE: http://fishingstatus.com/places/maps/instructions/lowrance
We now include a native Lowrance file with the extension .user in the downloads. Add this file to your SD card and you can import directly to your unit.
Here is a video on how to transfer the files for one unit to another, but at 1 minute mark, it shows how to import the files into the unit. Use those instructions for using the .usr file we provide in the download.
There are several different ways to convert the files for Lowrance. Depending on your unit, the easiest method is to use the Lowrance GPXtoUSR Geocaching Application. This application allows you to simply select the GPX files and it will convert it to a .USR file.
My favorite GPS software is GPSBabel. It will convert either file into several different GPS formats. It is free, and easy to use.
Another option would be to use the GPS Visualizer website to convert either the GPX or KML file to USR.