You will receive your temporary Plebe Summer addresses with your company assignment, probably mid-June. MIDS will probably be updated in the next few weeks; you can get it a few days sooner if you know a current mid (it won't make a difference). Permanent P.O. boxes will be assigned at the end of Plebe Summer.
I didn't bring anything other than the clothes on my back and the forms. For males, everything you need is issued.