Our rank structure is really loose. We don't have any structure for it, so it allows you to play your character how they best feel in your head, with some restrictions (not supreme apex of the military, but if you want to be a battalion leader? go nuts). Too much structure makes things less fun, and since its your story, why should your faction restrict how you want it to go?
So, basically, its just start writing, I always recommend going from a bit after your character signs up, and tell the story forward and backwards. Its hard to get someone to be hosting recruitment threads, at times.