Start with two layers. The image with the texture you want to add should be on the top layer and the main image should be the bottom layer.In the Layers panel, make sure the top layer (texture) is selected.At the top left of the Layers panel, change the blend mode in the drop-down menu from Normal to Overlay. This changes the way the colors in the texture layer interact with the colors on the layer below. Try out some other blend modes to find the one that looks best with your images.At the top of the Layers panel, experiment with decreasing the Opacity slider to change the look of the texture on the image