MapNav is not really a solution for people totally new to Unity, You need to be a programmer who is decently good at C# (since I use some advanced features here and there) and of course know how Unity works since you will be working with code and not some game-maker tool.
The documentation can be found in
Assets\Plugins\MapNav2\Docs\mapnav2.pdf. Browse there with your file browser since Unity will not show the PDF file in it project panel. That PDF will give you a higher level overview.
Then there are all the example scenes in
Assets\MapNav2 Sample. Run through them, check which one comes closest to what you want and study the code for the scripts attached to the various objects of that scene. I have commented them heavily to explain what is going on and why I do things a certain way.
All the scripts under
Assets\Plugins\MapNav2\ is properly commented and you will have to read the comments t learn what the functions does while you explore and learn to use the system.