I would suggest you search for the available literature and read the methods and materials sections to find how they performed their study.I hope so but I do not know what methods they used and it would be helpful (for me, maybe not for you) to know the methodology used and understand it. Despite my interest, I'm not going to go for university education about this now, just asking questions here can be helpful.
Again, a general Google search combined with Google Scholar can get you some, perhaps all of the relevant papers. If authors are attached to a university, they often have web pages associated with the university listing their publications and even providing free pdf copies. If you are seriously interested that is what it will take.
I could tell you how insect taxonomists determine and delineate species and make higher taxonomic assignments. While the concepts are much the same, the techniques for doing this with existing humans and human fossils will differ, so that would not answer specific questions about the methods used for determining the species of these fossils. I believe that @Subduction Zone provided more detailed information above on how it was done.