How to STOP growing?
If you are a male, I don't see the point in wanting to stop growing at 5'8.
If you are a female, I still don't see the point in wanting to stop growing at 5'8 unless its a superficial worry of not being able to find a boyfriend as well as others might because of some fear of being too tall for most guys.
Care to explain your reasoning? It seems illogical at the moment. While yes, I realize the only answer you are searching for is how to stop growing, but nonetheless, depending on the reason, it may be immoral or something for me to support you with your decision.