Here's how it works in a nutshell. Scientists write a paper that goes through the peer review process, and gets published in a journal. When the paper is published, the journal and the scientist's university will post a press release to EurekAlert! complete with information about the paper, contact information for the scientists and often photos and videos of the experiments or field sites. Journalists scan through the press releases, see one that catches their eye and write about it. Sometimes this process happens a few days before the paper is published, and all reporters vow
on pain of death to not publish their article until a certain time, when the paper itself goes public in a journal. The latter detail is a bit called the embargo system, and is why you'll suddenly see a flood of breaking news from many different outlets about the same study, usually all published the second an embargo goes up.