Why can’t I see my AirPort Disk over the network?
You can easily share all kinds of files across your network by connecting an external USB drive to the port on the back of your AirPort Extreme.
If you can’t see it or access the files for any reason, check it’s properly connected and powered, as well as unencrypted and formatted with either a Mac OS Extended, FAT16 or FAT32 file system.
In AirPort Utility, choose Edit > Disks and ensure the drive that’s attached shows up there. Also make sure Enable File Sharing is selected.
In Finder’s sidebar, the disk should appear under Shared. (Check ‘External disks’ is on in Finder’s sidebar preferences.)
If not, choose Go > Connect to Server from the menu bar, then enter your AirPort Extreme’s IP address (look it up by selecting the base station in AirPort Utility), then the username and password to access the disk, and choose the disk from the available volumes.