Here are some ideas for marketing a book you have published:
1. Contact bookstores to see if they will let you give a short talk about your book (and autograph copies while you're there, too.)
2. Check out radio stations---across the nation--that have interview shows where book authors can be guests. (If your book has a special angle of interest to the local audiences, that's a help, too.) Contact the stations, maybe first by email and then by phone. Send them some introductory info about yourself. As a radio talk host I did a lot of phone interviews with guests.
3. Look for book clubs (discussion groups) in communities. See if you can get yourself booked as a speaker.
4. Look for local civic clubs--they're always looking for speakers. If your topic is pertinent to their members, that's another possibility.
5. Look for public expos where you could set up a table, display your books, and (hopefully) make sales.
6. If there's an angle that is relevant to colleges or high schools, see if you can get booked as a speaker in one or more of their classes.