Press releases are a great way to announce the launch of a new book
Press releases give you the opportunity to start having conversations with potential readers even before the book is out.
Simply look at what other authors are doing and model your release after theirs. See how they describe the book, set the conversation and announce the release, then follow that model to write yours.
This is something you can have someone help you with too. You can hire a copywriter or delegate this to someone on your team to write and post your press releases.
I would go back and look at all the press releases you can find on books written about your topic, then model their success and ride it to your own.