Hi
I can't add to Picadie's great advice, except to say - please don't think that at 18 years old it's too late to do anything (except have your 17th birthday
There is so much pressure to make supposedly rest-of-your-life decisions at such a young age, it's absolutely ludicrous.
If you want to work in this area, you will. Voluntary work is a brilliant route to go down - you will meet like-minded people, be able to network etc etc.
Good luck