Even if it does sound logical, tournament is not an event. You should open the inventory and click on the phone - there should be the option to invite next ranked opponent, just like for chess tournament. Sometimes, your next ranked opponents is already on lot, and that option is greyed, and sometimes, game generate merchand or paparazzi as the opponent so you have to use cheats but that is rare occasion.
Once the opponent come to the lot, click on it and you should have the option to challenge it or something like that - make shore your Sim is not tired - it works the same as Spar option. I often chose Market, Academy or base camp for this (opponents will come to the lot you are inviting them from), but some places are quite spectacular to have fights on.
You can only do this in China, not in home town.