Hi
lbob,
There are numerous ways...here's one. Image > Adjustments > Levels. When you first open the levels dialog it will be set to RGB there will be three triangles below the histogram, black, grey and white from left to right. Move the black and white triangles toward the brightness values represented by the vertical displacement of the histogram until they just touch. Then, because there is a yellow color cast, look at the Blue histogram and adjust the sliders there, too. It is a simple method and yields good results. Adjust to taste. (I've exaggerated the results slightly)