Speak with Ambrose Boltspark at the Argent Tournament Grounds to become a valiant of Gnomeregan.
You've proven yourself worthy of competing under the banner of Gnomeregan, <name>. Now, you should introduce yourself to Ambrose Boltspark, who leads the Gnomeregan delegation. As the gnomish grand champion, he will enter you into the tournament on behalf of the city and oversee your training and testing as valiant.
It has been an honor working with you, <name>, and I wish you luck in the competition ahead.