How do I ask my parents for a autism assesment?

For about six months now I have thought that I have autism not serious but to the point were it worries me. My form tutor was the first to raise it to me and then my friends started saying the same. So a couple days ago I looked on the NHS website at symptoms of autism, I asked my friends about it and they say I have these symptoms.

So how should I ask my parents for one.

P.S. I think asking my dad would be easier if that helps.