Hi Geri! Welcome to Splitcoast!
Here's a link to a Poppin' Pastels tutorial:
Technique Challenge link
In my experience, this technique works best with light colored non-glossy cardstock and stamps that are solid images rather than outline images. Also, when you're applying the pastels, just dab your applicator up and down on the cardstock. Rubbing it across tends to smear the pigments in the pastels and doesn't look as good.
Hope this helps!