Texture layers have become hugely popular in the last few years and they are easy to use although you can get very detailed with them too. Some images may use quite a few textures with masks and different blend modes… it’s up to your imagination. The best way to get experience is to just start experimenting!
This image was a simple composition with two major colors. I find these work nicely with the blend modes because it’s easy to see what areas are most influenced. I dragged the texture layer on top of the original layer. At this point you will just see the texture. You can… and often it works better… to adjust the opacity of the texture layer for a more natural result.
In this case I left it at 100% and used the Color Burn from the blending modes on your Photoshop Layers palette. This applied the effect mainly on the green areas, leaving my main subject natural.