How old do you have to be to do flatland BMX?

I'm a 13 year old boy and but I'm really short for my age. I'm somewhere in 4 ft tall and I really want to do flatland BMX. I can't seem to reach for part of my bmx to do it because I'm too short and the bike is heavy! Is there a sertain age you have to be to do flatland BMX? Pkease and thank you! :)