If your base station or Time Capsule is connected to an Ethernet network, and you have a compatible USB printer connected to it, clients on the Ethernet network can print to the printer. This is known as remote printing.
Open AirPort Utility, 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.
Select the device you’re setting up, and then click Manual Setup. Enter the password if necessary.
Click Printers in the toolbar, and and make sure the printer is in the list.
Select “Share printers over WAN” to share the printer on the wireless device WAN port. You can also share the printer over the Internet using Bonjour.