To receive regular mail for Founders Program: use this address "Station F, Startup Name, Guild n°XX,14, rue Eugène Freyssinet, 75013 Paris". Founders mail will be delivered in a tray by Guild. Each Guild has a mailbox in its closest village. You are then free to come get your mail from your Guild mailbox tray.
For parcels: you can receive parcels in the post office located on campus, only if you are using a La Poste delivery services. If you want to use another brand such as UPS you will need to do it with a courier. You can give him this address "Name of the startup, STATION F, 5 parvis Alan Turing, accès par 55 boulevard Vincent Auriol, 75013 Paris" with your phone number. Then he can call you when he arrives so that you can get it. However, for security reason, STATION F staff is not allowed to receipt parcels on your behalf.