Without knowing your router/printer make and model here are generic instructions on how to share a printer on your home network. The computers that are going to share the printer need to be on the same network. This means you can ping each others IP address from both machines.
After I installed my new printer on the computer, I wanted to use it from other computers. I even wanted to print from my laptop computer, sitting on the patio, connecting to the network with a wireless NIC. Before I could do that, I had to share the printer. Windows XP doesn't automatically share printers, which is a good thing when you don't want to share your toys.
To share the printer, I opened the Printers and Faxes folder on the computer that was connected to my printer.
To open the Printers and Faxes folder
•Click Start and then click Control Panel.
•Click Printers and Other Hardware, and then click Printers and Faxes.
•In the Printers and Faxes folder, I clicked the printer's icon and, in the tasks pane, I clicked Share This Printer.
•I opened the printer's Properties dialog box, and clicked on the Sharing tab.
•I clicked Share Name, and then clicked OK.
That's it—the printer was immediately available for other computers to use.
Now that I had a network printer, I was ready to connect to it and print from other computers on the network.
To connect to the printer
•opened Control Panel, and clicked Printers and Other Hardware.
•I clicked Add a Printer.
•Instead of adding a local printer, though, I clicked Printer Connection and then browsed the network for the printer.
The whole process took less than a minute before I was printing to the network printer as though it was connected to the computer.