okgo to the layers(?)section. There's something that says rotate/zoom(not sure exactly) click on it. There'd a little wheel thingio try spinning it around. Look around and just try to figure out what your doing make sure its straight as possible.
Then, in the center( usaully ) where the image is the straightest look at a group of windows. You can pick one or a whole row or group, just try to keep itvstraight. Find the "select" tool, and drag it over the windows. Innone of the pull down windows selct " crop to selection ".
You should have a texture!!!!1!!one!!11!!¡¡eleven one¡!!1111!
Try fiddling around with it until you get it right, oh and please don't use my picture