If you registered online, then you only need to show up in time for your first event (3x3 first round isn't until after lunch, so if you're only competing in that, feel free to sleep in!).
If you do not register online, then you'll need to register at the competition. We'll be running registration twice during the day. It doesn't matter which registration you go to, just make sure to register before the first event you wish to compete in.