For me the easiest thing for me to do is create the route in google maps, save it as a kml file, and upload it into basecamp. The other program I use is the Harley ride planner online which lets you create the route in a gpx file and upload it directly to your gps or save it and open it up in basecamp so that you can upload it to the gps.

both google maps and Harley ride planner are much easier for me to create the initial route and just transfer it over.