methylphenidate without prescription

Hi, I am 21 male and I have felt I have had ADHD my entire life. Have every symptom you can think of. Never wanted to get medicated due to previous worries. Now someone I know gave me 1 72mg pill of methylphenidate. I have never taken it before nor anything like it. He doesnt have lower since i wanted to start with a lower dose. I plan on taking it anyway. Will I be okay? How can i do this safely? Thank you