There's going to be a lot of logic involved in this, so it'd be best to think about breaking it down into individual problems and solving one at a time. I'm thinking you'll need behaviors that achieve each of the following:
Detect when the player has jumped on an enemy and if the grab button is held down
Attach the two actors (enemy and player)
Launch the enemy when the player hits the right control
Determine when an enemy has been thrown so that, when the enemy collides with another, the enemies are killed
The first one should be the easiest, since it would only be a modification of the "jump on enemy" that the crash course walks you through. The others can be tricky, particularly if you're new to Stencyl and aren't yet familiar with how events work, how collision detection and collision groups work, and how animations are managed.