Here is the step-by-step photo tutorial on how to crochet bobble stitch.
You may get the complete wheat stitch tutorial in this link.
(Yarn over, insert the hook in specified stitch, pull the hook through the loop) 3 times,
yarn over, pull the hook through 6 loops on hook,
there are two loops on the hook remaining,
yarn over, pull the hook through 2 loops.
One bobble stitch made.