DudeCraftTo Cheryl in Comments:
Mod Podge isn't the best adhesive to use under glass. You'll get better results with a white craft glue like Elmer's. Remove only the pockets/bubbles of air. If you achieve an even layer of glue between the paper artwork and the glass (without air bubbles), it will dry clear. However, if you remove too much glue, it will dry with streaks or shiny spots.
Hope this helps!
Durwin
Hope this helps!
Durwin