I think your talking about a bubble jet printer. I have one too, and have done the same thing. This is what I would do.
You have to seal the printing, or else it will smear when glue, or any moisture for that matter, touches it. You can buy a can of Art Fix Spray, that is used to fix charcoal drawings, or use Dull Coat to seal the prints. To much money for me, What I did was to use Scotch Brand Magic Tape to seal the printing behind a thin plastic sheet. The magic tape is best for this I found as it all but vanishes once applied. Then the sign can be cut to size and stuck to the window with a drop of white glue. Once I used clear box tape to secure the poster to the window, covering the entire window with the clear tape. I've used clear box tape to seal bubble jet printing before too, but this dose put a shiny surface on the sign. That's the thing with the magic tape, it has a flat surface when applied, but it's not good to apply the sign to the window because it is not clear on it's own.
TrainClown