How Harrogate ranks work?

I’m going to Harrogate next year for paras and really keen to learn all there is to know and be the best I can be. I’ve seen some of the guys at Harrogate with a junior rank on them (not sure what they are called). Just wondered if anyone knows how you can achieve this and if anyone knows anything about this I would love to know 👍🏻 (hope this question isn’t a rule breach on this page)