There is no easy answer. I was always reclusive. But I had little in common with anyone and was, perhaps, a bit shy. I was always the smartest kid in the class and never had to do any homework to achieve that... so I considered most other kids to be rather dumb. They didn't seem to know much of anything and had no interest in the things I was interested in. I guess I would have been considered a nerd.
I found Sea Scouts fun. When I was younger I was quiet but in a couple of years was a patrol leader then troop leader. I found it easier if I was the boss and still have that attitude.
It's all part of growing up. After I joined the navy I went to officer school and learned that if you act like you're in charge people will be inclined to believe you are.
So it takes a bit of time to learn self confidence and realize you are as fit and good as anyone else and there is nothing to fear.
If you have a talent, showing it will often attract admirers and that can break the ice.
Being clean and dressing well is important.