The flat, smooth part of the stamp sticks to the acrylic block. Yep, it's a lot like a window cling.
Press it down on the ink pad.
She'll need to be careful to only ink the rubber stamp because if she gets ink on the block, it'll transfer to the paper and ruin the picture.
When she's done stamping, just wipe the ink off the stamp with a baby wipe or a damp paper towel. Since there's no foam on the back of the stamp, she can even run the stamp under water to wash it off.
If she wants to use more than one color on the stamp, she can use regular markers (not Sharpie's) to color the image however she wants. Before she stamps the image on the paper, have her hold the block/stamp up near her mouth and huff on it. Kind of like people do when they're cleaning their eye glasses. That will re-moisten the ink.
If the ink stains the stamp, try washing it off with a little bit of rubbing alcohol on a cloth.
Barb