This reply is for William:
This may seem obvious, but first you need to know what newsworthy or noteworthy accomplishment or event you want to notify the press about. Once you've got a topic, you'll want to hire someone adept at writing press releases. There are certain elements and phrases that will make your PR more likely to be read, and circulated.

Once you've got your topic and writer secured, you'll want to get a subscription to a PR site. There are a variety of PR engines, and you'll want to do some research for the best one that suits your budget and your industry. There are some free options for pushing out PRs, but in my experience these don't get the visibility most people are looking for when they craft a PR.

Once the PR is published, do some online listening. Check to see where it's been picked up and link back to those sites, ideally via your website and social media channels.

I hope this information is helpful. Get in touch if you'd like assistance with this and good luck. Thanks to Juan Manuel for starting the conversation.