you will receive your company assignment in June, prior to your arrival on I-Day.
Informational:
Your summer assignment may appear as O-27, or O-28 for example- meaning you will be in "O" or "oscar" company for the summer (which combines plebes for both 28 and 28 companies), however at the completion of plebe summer, when the Brigade reforms, you will align with your assigned company- 27 or 28... and "O" or "Oscar" gets put away until next summer arrivals.
Alpha: Companies 1 and 2
Bravo: Companies 3 and 4
Charlie: 5 and 6
Foxtrot: 7 and 8
etc...
P is the last summer company, and will break into 29 and 30 following reform.