I am not an attorney, certfied public accountant, business
consultant, etc.
I suspect you would go about starting a publishing company,
like you would most any other company.
1. Go to college, and major in Business Management, and/or
2. Get a job with a local newspaper publisher, and/or
3. Look for books in library/bookstore/internet with
subjects/titles "How to Start Your Own Business", and/or
4. Contact a public accountant, and/or attorney, and/or
business consultant.
As a starter, read all of the threads or search threads in the
following FREEADVICE "Starting a Business" forum, using
keywords such as "publish*", "music", and "news*":
https://forum.freeadvice.com/forumdisplay.php?s=&forumid=3
Citizen Brown