The BBC has a web site just for youngsters who want to start or try. Dont know the exact details but at your age you will find it quicker than me. Start at BBC 2012 . . .
Ur not just going to be able to enter. Their is a process that u need to build up. Are u part of a club? Coaches put forward names and the year before the Olympics will be the trials. If u r fast enough ur will be entered into the trials and if u get into the top 40 or so places u will be in the Olympics.
First you would have to be really good and practice for hours a day, then you would have to join teams and compete, then get noticed at a high ranking championship, like nationals or regionals.
Call Lord Coe on 020 7842 5700 and ask for an information pack.
GO here http://www.british-athletics.co.uk/ look up your local club, go along and do everything they tell you, train hard and then train some more and hopefully you might get picked.
hi I am 13 years old and I want to be in 2016 team GB for running. can you please send a link or something to help me get into it. it will help lots.