Little or no experience with RPG's and none with hero? Are you insane? Trying to teach basic RPG, the basic hero system, and start a new adventure in one afternoon...
Try a quick and rewarding dungeon crawl with a handful of interesting NPC's.
Let them kill stuff. Insert a good quick hack and slash with a bit of a challenge.
Have a traveling minstrel of sorts acompany them and then have him/her regail crowds with tales of their adventures in a heroic, nearly fantastic light.
Create a clear antagonist, like the classic dark priest of the necromatic arts (remember that they will not have run into two or three hundred of these before, as most of us have).
Reward the PC's with things most apealing to teenagers.
And, most important, make sure they have fun with it.
Just a few suggestions,
-Preston