I'm assuming you don't have file sharing / printer sharing set up on your computers, so let's set that up first
In XP, go to the control panel, network setup wizard and go through the screens to set up your connection, computer name and workgroup. The next screen asks if you want to turn on file printer sharing. Turn it on, click next and apply the new settings. You'll have to do this on all computers on the network. If you aren't using XP, the procedure is more or less the same - search Help and Support for file sharing.
After rebooting, you can open up the control panel, select printers and faxes, right click...add a printer. This opens up a new wizard. Select network printer, browse for printer and it will bring up a list of computers and printers on the network. Select one and go through the next wizard that might have you installing a printer driver to the remote computer. Search Help and Support for printer sharing if you are having problems.
You'll want to secure the wireless router by setting up WEP or WPA encryption, as well as a wireless filter if you haven't done so already. The routers manual will step you through this. You'll now also have the abilty to share files with your network by putting them in your Shared Documents folder in My Computer. You can also share whole folders by right clicking on them, selecting Sharing and Security and setting the folder to shared. Keep in mind though, that if you don't secure the wireless network, outsiders can access these files, use your internet connection and even worse... waste all your paper and ink
Good luck man09