How can i free myself of the fines and charges i am facing?

As my first offense, i was charged with possession of under 50G of marijuana and possession of paraphnela. My 'friend', a minor, was actually the one resposible. He brought the drug into my car and smoked without me present or knowing. As i went outside to get my charger from my car, I noticed smokey windows. My friend had broke into my car and smoked marijuana inside of it. I argued with him, telling to get out and that he was very dissrespectful for doing so. At this moment a cop showed up and arrested us both. i told the cop it wasnt mine but he said bring that to court. I am pleading not guilty and will tell my story, to the judge without an attorney, Will i possibly be freed, not guity and free of penalties?