There are a few ways to make a light.
make a blank layer above your image
on the blank layer use a brush at zero hardness
paint black in the area where you want lit
on the same layer, change the color to white and paint over the black
change the layer blend to overlay or softlight, adjust the opacity, move the layer around to yor liking
Try this whole procedure with a different color over the black. play and experiment to find the effect you like