Here is my caveman usage of tracks on a Nav VI (or V and similar). I’m sure experts can drone on in depth, but if you just want to display a track on your map so you can follow along on a ride:
Send the file to the device (.gpx), doesn’t really matter if you use Basecamp or just copy the file. You can even receive it from another bike over bluetooth.
The, select a track by going to:
1) Apps -> Tracks
2) From the list of tracks, select whatever track you have in mind.
3) That will take you to a preview of the track on the map.
4) Click the wrench icon (upper left)
5) Click the “Show on Map” checkbox. You can also set the color of the track that is show on the map, as well as “Convert to Trip” which will make a route (of sorts) out of the map. I never really use it, so I’m sure someone else can chime in. I just select “Show on Map” and go back to the home/map screen.
That’s about it. Also, if you don’t turn off “Show on Map”, it stay there pretty much forever. Doesn’t hurt anything, but if you see a random track from a past ride while out riding one day – that’s the reason.