For public speaking, you can join a toastmaster's group to practice. There are many local chapters. Watch TED talks on topics you want to speak about and people who are highly successful.
For podcasts, watch some successful podcasts in the areas you are interested in. After you choose a topic you want to speak about, do them on a set and regular schedule so people will expect them and you will build a following. Promote them on your social media platforms and ask your friends to give you likes and shares.
What else do you want help with?