Compete in a local bowling league. Go to your local bowling alley and ask about signing up with a team or starting your own team. Verify that the alley holds at least 36 games per season in the league and that the alley uses the Professional Bowlers Association official oil patterns on the lanes.
Contact the USBC [800-514-BOWL (or 2695)] to find other leagues nearby if your local alley doesn't have any participating.
Play at least one full season with a team in a bowling league. Keep track of your scores, as one way to become a professional is to have averaged at least a 200 or better over all games in a season. You'll need at least a 190 or better average if you play in a USBC league.
Visit a regional PBA (Professional Bowlers Association) tournament in your area; check the schedule in the Resources section. Sign up and compete in these regional events. Cash in at least one event to become eligible to sign up as a professional.
Fill out the PBA application form after you either have earned the minimum average in a league season or won at least one regional PBA event. Find the form in the Resources section. Include your membership fee of $300 with your application.
Wait for your membership to be granted. Begin competing in as many PBA-sanctioned events as possible to up your stats and cash in on tournaments.