How do I become a mentor for newcomers in the community?

You become a mentor mostly by showing up consistently and being patient. You do not need to be an expert; you only need to be a step or two ahead of the person you are helping and willing to answer the same beginner questions without sighing. Start by hanging around after meetups for one-on-one questions, because that is when shy newcomers ask the things they were too nervous to raise in the group. Walk someone through their first wallet setup, their first contribution, or their first node. Point people to documentation rather than just answering, so they learn to find answers themselves. Mentoring is the quiet engine of community growth: most active contributors got there because someone sat with them once.