Whoops, sorry, I didn't read the tutorial before replying.
Anyway, the problem there appears to be that they're telling you to apply the texture directly to the box, which I don't think is a good idea.
Rather than that, what you should do is this:
1. Apply a "Mesh Select" modifier to the box and select one side of the building.
2. Apply a UVW map modifier.
3. Open up the material editor and apply the material. Make sure it is applied to the UVW map rather than the building itself.
4. Change the size of the UVW map, and move or rotate it around (by clicking on the little plus sign next to the modifier and clicking on 'gizmo') until it the part of the texture that you want is on the correct part of the building.
5. Repeat this for each face of the building, each time applying a mesh select modifier.
Hope that helps.
