You read them in this order. 1 then 2 then the boys Nam, Jin, V, Hope, Suga, Jimin, Jung then back to the main parts. They all tie in together. The ones labeled with the boys names are just her getting to know the boys since they had just recently meet at the cafe. The Suga one has important things to the story as does Jungkook's one. Jungkook's sets up part 3.