Through a yogic process of meditation, reflection, and austerities, one progresses through these stages of enlightenment until spiritual liberation.
Along the way, one can become a kevalin, or knower of kevala jñāna, without necessarily advancing to the final stage of becoming a tīrthaṅkar (one who has reached the end of karmic existence).
For instance, according to Jain tradition, Mahāvīra had a disciple named Gautama who attained the level of kevalin following Mahāvīra’s death. However, he did not go on to become another tīrthaṅkar.