I would just try experimenting with the effects and various layers and opacity levels of the layers. For example I would suggest duplicating the original layer - you'll find that option by right clicking the layer in the layer menu or clicking the little left pointing arrow at the tops of the layer menu.
On the top layer, I would then adjust the color levels under the image menu at the top of the screen by selecting 'adjust' and then trying different options. I would then lower the opacity level of the top layer and adjust the layer mode by selecting from the menu that reads 'normal' at the top of the layers menu. I would recommend the option 'burn' or 'color dodge'. You can also try running different effects such as craquelure and etc found under the 'effects' menu.