Purchase one of the many wireless routers which have a USB port for a printer. This is a feature to look for when purchasing a new wireless router, as it allows for better flexibility (and price) than other methods of printing from a wireless network.
Install and configure the wireless router. The wireless router must be functioning correctly before you can effectively print through it.
Plug the printer into the wireless router by attaching the printer's USB cable into the USB port on the router. All computers that have previously used this printer must now have access to the wireless network or a bridged wired network to continue being able to print.
Purchase a printer with a network port, a port that is designed to be used in networked environments. This feature is primarily for printers designed for use in an office environment, so this solution is likely to be more expensive but more flexible.
Install and configure the wireless router to your computer and network.
Connect the printer's network cable to a wired port on the wireless router. This will also work if the printer is on another attached network.
Install and configure the printer on a computer that has WiFi or is connected to the wireless router.
Ensure the printer is working correctly.
Install "File and Print Sharing" on the computer with the printer. This will allow the printer to be shared across the network. However, the computer with the printer will have to be on in order for wireless clients to print through the router. It's not the most flexible solution, but it will work with existing equipment.
Click on "Start -> Control Panel -> Printers and Faxes."
Select the printer to be shared and right-click on it.
Put a check mark in the "Share This Printer" option and give it a descriptive share name.
Click on "Start -> Control Panel -> Printers and Faxes" on the computer that needs print access through the wireless router.
Select "Add a Printer," then hit the "Next" button.
Choose "A Network Printer" and hit the "Next" button again.
Click "Browse for a Printer," then "Next."
Find the printer you want to print to, then click "Next."
Follow the instructions on the screen to finish setting up the printer.