Ok, here is something probably very simple that I can not figure out for the life of me. It has to do with gradients, and adding them as like an "overlay layer" to a photo. I have looked everywhere for a tut and have found nothing, so I am assuming using gradients is very basic and I am just stupid. If any one could help, PLEASE do!
Below is an example of what I am talking about, the first is the original pic, then the gradient, then the result.