Editing Texture Maps of Polygons

[domcarminefilix]

Ok so when I first get in and import my model I go to one of the polygons on the model and I right click into "Open Material Editor" and I go to "Texture Maps" to change the texture. My problem here is that it will not let me change the texture at all, it is grayed out and won't let me touch it.

Any Idea on how to fix this so I can change the texture?