Hello there and welcome. I hope you enjoy your stay here.
Jericho will most probably come and explain the forum and its basics in a couple of minutes? maybe...
About the Youngster thing.
It changes on your posts counting. And also you can change it with a shop item. Which is expensive. I think, Havent tried it.
Also to buy that item, you need rupees. You get rupees with posts. Thats it I think.
Welcome!