3D texturing : problem import images

Hello, I have a simple problem to explain, when I create a 3D object with a .obj file (a cube), the cube is in charge there is no problem, but to my surprise I can not import texture such as customizing ".png" or ".jpg" because if I did that, the texture is absolutely not visible, only the colors of the image editor works for texture. For example I fill my pink image of the image editor, and the cube turns pink, but if I import an image, the cube becomes gray but that's all.

Is there a reason for that?

Are you sure you've exported/saved the model with proper UV mapping?

I did not do what you say because I can import my texture in Construct, my object is simple (a cube) I wanted to test what would a stone texture on it but it does not work.