I want to mail a letter to a person there, when can I do that or do I have to wait to get a formal letter from that person?

In addition to the question. What format is the address for recruits? General format please

Get with their recruiter on the Friday of their first week to get your Recruit's address. Then send letters and send them often even if you dont get any back. Those letters mean so much to your recruit. ENCOURAGE, ENCOURAGE, ENCOURAGE!!!

If you know the company or platoon you can do it now.