I started at 12 with a long board - - which I got by trading a guy for my train set. Anyway I learned everything I could from a few buddies who had jobs at the O'Neil's Surf Shop in Santa Cruz, CA. Pleasure Point was where I started, and I got up the nerve to get up pretty quickly - - - - after I noticed other guys were getting waves and I was missing out.
Honestly.. i think it was my first or second try. I was probably 22 in Santa Barbara, on a longboard, don't know the size, but I think all those years of yoga helped my balance. I'll always remember that.
When I teach people I won't put them on anything smaller then a 7 foot, with a 6'2 you might as well ride a patoto chip in the lineup. Starting bigger increases the boards bouyancy, therefore making staying afloat much easier when treading for the perfect wave.
But, back when I was 13, rode my first wave, it was after 2 full days in the water without any stopping. I felt so accomplished.
At 45 years old, I took a surfing lesson with an expert, older guy. I got up on the first try. It was a 9'soft-top longboard. You might want to change out the fins on that board, for a longer single fin, for a quick way to help you stabilize. Good luck!