First you need a Kaleidecolor ink pad. These pads are like 5 small individual colors that stay seperate while in storage, but slide the lever and they snap together when ready to be used. They come in a number of color combos!
Roll your brayer over the pad to ink it up.
The cardstock you use MUST be glossy cardstock! This is very important... the technique doesnt work if you use a regular piece of paper. Roll the brayer back and forth over your paper to get an even coat of ink. You may even need to re-ink your brayer and do it again. You will get a very pretty rainbow effect. I like to stamp an image in black, usually a solid image works best.