How does one become a yogi?

Buddhamaitreya.org. The yogic path is an ever-present choice within humanity. Buddha Maitreya the Christ is the reincarnation of Babaji, and has had recognitions and enthronements in every major TIbetan Buddhist lineage.

I would start by reading "Autobiography of a Yogi" by Paramahansa Yogananda ... who this movie is about. It's a good place to start; I need to read it again. Also the "Tree of Yoga" by B.K.S. Iyengar.

You may find it to be something other than "the serene life". BUT, the serene life is supposed to be an inner condition, not necessarily external, as per Yogananda's writings. Try locating and taking in some local yoga and/or meditation classes.

I would also suggest that, after reading the Autobiography, contacting Self Realization Fellowship for their lessons series. (I am not touting them out of ego or anything. But that's the only other thing I can humbly suggest, in case it is an appropriate path for you. You have to experiment and find the right temperature and context that suits you.)

You study more and you'll find Yogananda was fraud ...just an ordinary man.
Best recomend books to start a yogic path I can suggest "Complete work of Swami Vivekanada"