How can I contact a soldier at fort benning, ga?

My brother left this weekend to attend basic training at fort benning. He was able to call us yesterday, and said his training doen't start for nine days, so I'm guessing he's going to be in reception. That was the last we heard-I want to send him a letter, but I'm not sure of how to address it. Should I wait to get more info from him, or can I try to contact him? Thanks