HELP!

Hi! I've been working on this tutorial: Click HERE

and I'm stuck on how to make the little dialogue box. The writer says to use "stroke" but I don't get it...can someone explain this to me like i'm a 2 year old so that I can understand it.

I'm nearly done!

ACK!

EDIT: FIGURED IT OUT!!! THANKS TO EVERYONE FOR HELPING OUT MY DUMBASS!!!!