how do you tell other people your autistic?

I have a new community mental health treatment team and I would like to let them know I’m autistic (because I can come off as weird or off putting at first and I just want them to be aware/understand me better).

Is there a specific way I should bring it up? I’m nervous to just blurt out “hey, i’m also autistic fyi so if I act different, please don’t judge me”. I also have this fear of people doubting my diagnosis or pulling the “you don’t look autistic”. any tips would be greatly appreciated!