How do you start battling in the Olympus Coliseum?

Walk up to the big block and try to push it.

Walk up to Phil and press talk.

When you first start the game you have a choice of where to go.

Go left to the Olympus Coliseum. When you get there go into to Phil, talk to him, try and move the pedastal, go back and talk to him.

Then you'll get some training missions to do.

Do them, beating the best time (I belive it's 18 seconds for the first and 1minute for the next).

Then you'll try and enter the games and Phil won't let you.

So go outside and Hades should talk to you and give the entry pass.

So go back in and talk to Phil. He should then let you into the games.

Okay first talk to Phil he'll tell you to move the pedestal over by the wall.

Then after you try and move it talk to phil again.

It has nothing to do with the white or yellow trinity, because you need to go to other worlds to get those trinity.

But follow what I'm saying. Push the heavy block near the yellow trinity, keep on pushing until sora says it's too heavy to push or something like that.

After he says that then talk to phil then he will tell you that you are not a hero so you can't battle.

So exit the are where phil is and you'll enter a sequence where a guy gives you a pass to enter the battles then when the sequence is over talk to Phil.

Then you enter the premilinay battle, clear those then you enter the real battle. Good luck with three headed dog!!!