Adding an Effect to an Image

1. Open an image.
2. Create New Channel.
3. Using circle marquee, draw a circle which imitates halo.
4. Select > Feather. (Radius = 15 for my example). It's imperative to use Feather feaure here to simulate halo effect and soften the edge.
5. Delete to clear inside the circle.
6. Deselect the selection.
7. Select RGB to see all of the image.
8. Layer > New Layer.
9. Select > Load Selection > Channel #4 where the halo is drawn.
10. Edit > Fill with color to apply a color which simulates halo.
11. Adjuting Opacity will complete the effect you want to see.