If your base station supports it, you can connect a USB hard disk to the USB port on your base station, and computers on your network (both wired and wireless) can connect to it to access, share, and store files and data.
Plug the hard disk into the USB port on the back of the base station. Open AirPort Utility, select your base station, and then choose Base Station > Manual Setup. Enter the password if necessary. Click Disks in the toolbar.
Note:If you’re using a Time Capsule, you don’t need to connect an external USB hard disk. Time Capsule comes with an internal AirPort disk. Use the following instructions to set up disk sharing on your Time Capsule or the hard disk connected to your base station.
AirPort Utility is located in the Utilities folder in the Applications folder on a computer using Mac OS X, and in Start > All Programs > AirPort on a Windows computer.
Click File Sharing.
Choose “With a disk password” or “With base station password” if you want to secure the shared disk with a password, or choose “With accounts” if you want to secure the disk using accounts.
If you choose to use accounts, click Configure Accounts, click the Add (+) button, and then enter a name and password for each user who will access the disk.
Choose “Not allowed,” Read only,” or “Read and write” from the AirPort Disks Guest Access pop-up menu to assign guest access to the disk.
Guests will have access to the hard disk, but not to the user accounts.
Select the "Share disks over Ethernet WAN port" checkbox if you want to provide remote access to the disk over the WAN port.
If you connect a USB hub to the base station, you can connect multiple hard disks to it, and access them from the wireless network.