If you press the "open in window" button it opens the wordle in its
own window (OK that was pretty obvious). What's interesting is that
you can resize this window to whatever proportions you want. So for
example you cam if you make it banner shaped. Pressing randomize a few
times will eventually give something useful. Its not perfect and it
certainly doesn't always fill the box you have created but with trial
and error you will get something useful.
You will then need to convert it to a picture file by using print
screen and pasting into your image editor.