Gather your stuffs. You will need:
a sharpi marker or any old permenant marker
puffy fabric paint (i used tulip brand)
acrylic metallic paint (i used plaid "folk art")
a foam brush
a stained glass pattern ( i obviously hand copied mine off of an internet search for "stained glass pattern")
To start, clean your window. It can be any glass window. I did this on GLASS not plexiglass so I only know that this works on glass.
( Dont be afraid! I have done this once already and I cleaned it off with soap and water 5 months after I painted it. So it is perfect for renters or commitment worriers). Get your sketch.