If you want to submit a local press release, read the local papers. Find reporters covering your subject. Many papers now publish the reporter's email address. You should send relevant news releases to the appropriate reporter. Make sure it is news. Mention how your subject relates to the topics they cover. Send your release in the body of your email not as an attachment.
If you want to distribute a regional or national news release, look to any of the news release distribution systems.and follow their submission instructions. I've had good luck with dbnews in getting into Google news with no cost for submission.