You need a piece of Cut'n'Dry Foam the exact size of your stamp block. (You can also use Cut'n'Dry Felt)
Stamp the image on the foam using Staz on ink. Then, with reinkers, ink over the areas you want to colour. For instance, on the Razzle Dazzle image I used below, I coloured the flowers and leaves different colours. Don't worry if the ink spreads. Your stamp won't pick it up.
Then, use your pad to stamp! You might need to refresh the ink occasionally. Because the pad is the exact size of the stamp, your stamp is automatically positioned to pick up the right ink.
If you want to keep the ink pad, slide it into a baggie, and label the stamp it goes with on the bag. Because, the ink pad doesn't really resemble the stamp!