Just wondering, cause I've never entered one and I registered to the enter the one that is coming up in a couple days.
I entered too and this will be my second. It is quite like a random matchup and an opponent is selected for you. You just have to keep on battling and winning so your rating goes up. It is nothing like the Pokemon league in the anime, you just have to get a high enough rating and the highest wins the tournament. Results can be seen on the global link after the competition ends.
Hope this clears it a bit.