Seeing Psychiatrist tomorrow for diagnosis

I'm going in for psychiatry tomorrow. I'm trying to get a diagnosis for ADHD and for another thing I've been struggling with.

My PCP told me to get checked for ADHD 4 years ago but I put it off. I'm ready now and I'm 100000% certain I have ADHD. Anyways, I'm not sure how to bring it up, or what should I say. Any advice for anything? How did you guys bring it up to your psychiatrist?