How could you move from England to New York City ?? ?

I want to move to New York City and I live in England how could I go about moving?? I'm 16 and I live in England. I want to know what the age for moving to the USA alone is and how I could get a job and what is the process for moving out there? I have friends and family living in Washington DC and Buffalo, so would I be able to get a sponsorship and move to New York? Also my mum told me that you have to do a quiz/ knowlege thing to move out their to get citizenship.