If I was you, I'd wait. Teenage years aren't the time to be going making massive decisions about yourself and who you are, because no matter how sure you may be, it's still a screwy time of life. Hormones going nuts, school, college, life in general. There is enough pressure as it is without adding to it.As for when and how, that's only something you can decide, people can give advice but at the end of the day you and you only know when the time is right. You have to be totally comfortable with yourself and who you are, totally comfortable talking openly about it. You need to take into account parent's circumstances as much as reasonably possible, like if Mum is having a tough time at work, you don't want to be adding more to her plate.Either way, it's not something you just do because the mood takes you, you really have to think about the decision that you are making, the reaction it may cause, things like that.Until then, just enjoy life, be yourself, have fun, see people and generally be happy. When the time is right I'm sure you'll know.