Rank C qualifying round is the same as each round you've been in before - again you will select a 3-man team and you will assign a single fighter to each of three rounds. Your job is to finish all three rounds by having the highest amount of Battle Orbs. The difficulty level of Rank C qualifying round is almost the same of those before it - you should have no trouble with dealing with the enemies.
After finishing this round, you will be automatically enlisted to the preliminary round - to take part in it, speak with NPC in C Rank Tournament Reception again. Before you do so, however, you can take part in two additional Ally Events - "Tiny and Rare Flower of Value" and "The Way of Food". If you are interested, go to the "Ninja World Tournament - Ally Events" chapter to find detailed information about them. It's worth to visit local stores, where you should find some new, useful items.