How did Carlisle meet the Volturi?

he was once part of the volturi

well decdes ago it says that he lived with the volutri for a while then decided to go his own way but he was just friends with aro he didnt like there style like how they killed but he respected them

Carlisle was studying in Italy when he met a coven of vampires called the Volturi that seemed more civilized and educated than those he was familiar with in England. Aro, Marcus, and Caius were the three vampires that inspired some of the works of Solimena. Even though they were refined, they persisted in trying to persuade Carlisle to drink from humans. Naturally, he refused.

You can find his story in Twilight chapter 16.

Carlisle first met the Volturi when he was studying medicine in Italy and he stayed there as a member of the volturi guard but he grew tired of their way of life. This clan was much more civilised than the clan who were hiding out in the London sewers.