[How to fade out a part of a picture]

Hey guys,

 

I need again help. Anyone a idea? I would have some area´s of my picture like this:

 

 

[How to fade out a part of a picture]

Thanks

[How to fade out a part of a picture]

Hey i have a question is there any way to create this effect that is marked in the picture and is all around the map with paint.net and can u explain me how to create this effect if it's possible?