Your USNA plebe summer mailing address will be sent to you a few weeks before I-Day. You can put together a care package of compression shorts (navy, white or black, but preferably navy so they "blend in" with your PT shorts), along with whatever else you want to include, and send it to yourself a few days before you leave. If you bring the shorts with you to I-Day, there is a strong probability that they will be taken away from you and you will not see them again until PPW, so it defeats the whole purpose of having them for Plebe Summer. I think I sent about 3 or 4 pairs of compressions to my plebe. Not sure how many he actually needed.