Once you arrive in Yu'Biusk, a matradee goblin stops you and asks you what you are doing here, after explain the reason you will be directed to Zarador who you will find if you follow the path around the spire. You can refresh your supply at banks around Yu'Biusk anytime during the quest.
Zarador will explain the rules to you regarding the tournament. No summoning is allowed during the tournament. However, each round will include a special limitation or mandate. You will be told of any extra limitations before the round starts.
You should head to the Dorgesh-Kaan camp now, which is west of Zarador down the two ladders to find My Arm, Burntmeat and Grubfoot waiting for you, here to cheer you on. After going through all the talk options, a Goblin messenger appears and gives you information on your first round competitor who ironically, is Yelps. It turns out that this is no Goblin at all, he is a level 140 Human Infiltrator, who is not happy that they have been excluded from the tournament despite being Bandos followers. He will then attack you.
After dispatching the Human Infiltrator, you will read a note on his body, which states that there are 5 more infiltrators, each planning to poison one of the champions, they are using Goblin Type 3, which is a Goblin wearing a battered top hat, so that they can easily identify each other.
Return to Zarador, he tasks you with dealing with the infiltrators, since they are human and therefore your problem. Since they all wear battered top hats, it shouldn't be too hard to find them. You will find the Human Infiltrators at the following locations: In the middle of the crossroads, Ork Tower, Goblin Cleaner next to Yelps in the Goblin Camp, Troll Tower, Guarding the secret weapon, Dead end south of Orge Tower.
Once you have defeated all the Infiltrators, return to Zarador to start your first match against the Goblin champion, Yelps. The special rule for this round is that you can take as many goblin minions as you like, being that all the goblins are rooting for Yelps, it means he gets bodyguards. Make sure you kill these first. Yelps will often bring them back into battle. You cannot damage him while they are still alive. Every so often Yelps will do high damage whilst teleporting around the arena, coins will appear wherever he is about to teleport to, so stay away from that section.