Honestly, don't try to conceal the fact that you're new to tournaments when going to an event. Allow someone to help you out wherever you need it, as it'll make things a lot less confusing. Check out this video [
https://www.youtube.com/watch?v=YePIBypk_DI], which takes you step by step playing a legit tourney match. And let yourself know that there isn't that much on the line if you lose. Just set a simple goal for yourself for your first few tournaments. For example, perhaps try and just take a game off a player. Then next tournament, try and take a set. Don't feel bad for going 0-2, because it's probably gonna happen. It's happened to every player at some point. I know firsthand that Smash events can hold an oddly intimidating atmosphere. But a good T.O wants everyone to have a good experience so if someones a **** to you for being naive, then either brush it off or if they take it too far let a T.O know. Everyone is there to play the game they love, and have a good and comfortable.
tldr; let people help you, don't feel bad for losing, set goals, be relaxed and let it be a learning experience, also click that link