Basically how I do this is, when im in blender I create a new image texture material, choose the texture your using, if your looking for just a plain colour like your green brick well heres a texture
so then your brick will probably be lots of mad colours and look very weird, but thats okay because then you switch to your UV Editing tab, and go into edit more and press A, this will select all your faces so then at your uv editing menu on the left, hover your mouse on that tab and press A, it should have some type of 2D version of your model, then you can press G to move your little 2D version and press S to scale it, to get just a plain colour you can press S until its small enough to fit into which ever colour your want, if you dont understand this feel free to private message me!
It should be relatively simple. You need to export the texture then add the texture in the mesh. I believe you use a .mtl file to do that if you exported your “Brik” as a .obj.