Originally Posted by Genaro

Garmin connect now has a route creator feature. I haven't used it yet, but I would imagine it would be the easiest to use. Just register with garmin connect if you haven't already, go to courses, and click on the create course icon - create your course hit save, and send to device
That simple! Test it out with small courses first before you go on your first epic journey and have a back up like a map because things do go wrong some times.