Hi...I have a little experience with this!
My oldest DS was selected as a sports ambassador (baseball) when he was 15. From what I was able to gather, it is a nomination process either by a coach or teacher. I was never able to find out who nominated him.
We went to several meetings before we/he decided to make the comitment to go. There were different locations to choose from and DS chose Australia. We had a lot of help in fund raising suggestions and was able to raise the money for him to go....yes it is expensive.
He was gone for 2 weeks.
It was a great experience for him. His team was made up from young men and coaches from all over the country and they played several tournaments while in Australia. There was also time for touring and it was well chaperoned.
Any other questions? I'd be glad to help...