First, tell your closest people.
See how that goes.
See your doctor and you are likely to be asked why do you want to be a woman?
As questions go that is a doozy.
Then you may be referred to a psychologist of some sort.
Maybe a gender specialist.
I would be looking at keeping my job for a couple of years at least.
If you do not have a job now you are not going to obtain one as Kim while you are still mostly boy.
You are looking at living full time about three to four years down the track in my opinion.
First tell Mum and then see where your questions go then.
One step at a time.