You can find great instructions and many pictures on Trish's site.
Heat your iron, touch an oil pastel on to the hot iron.
Iron melted pastel on to parchment paper, moving the iron around.
Continue adding more colors to the parchment paper in the same manner until you have a large pool of harden pastels. Trish had a much thicker pool of the melted pastels on her parchment. My pastels seemed to just spread out instead of piling on top. I wonder if it's because I'm using water soluble oil pastels? I used a mixture of blues and some purple oil pastels.
Place a piece of card stock face down over the hardened melted pastels. Iron the back of the card stock to re melt the pastels and transfer them to the card stock.
The top piece of card stock was used to clean the melted oil pastels off the iron, then placed down on the melted oil pastels on the parchment to pick up more of the oil pastels. The bottom piece was use as described above.
Did another sample using a mixture of colors of oil pastels and black card stock.