Go ahead, you don’t have to be the best player in the world if you want to go for a tournament. Even if you don’t place as high as you’d like to be, losing gives you more opportunity and feedback to improve as a player rather than just solely winning. Everyone began at one point where they weren’t great, but later became good. You will improve overtime as a player as you play more and more people since they’ll show your weaknesses and flaws that will help you improve.
For starters, you should use websites like smash.gg to find tournaments near you, and other social media networks like Facebook to find pages where they hold locals around your area to play other people.
If you can’t find any tournaments or locals in your area, depending if you play Smash 64-Project M, you can use tutorials online to help set yourself up to play on netplay against other players. I don’t see you having an issue with Ultimate, since it’s the latest smash bros title released.