The specific model not provided with Full Feature software for Mountain Lion which mean the only way to set up the wireless connection for the device from a Mac is creating a temporary ad-hoc connetion (direct connection between the printer and the Mac) and using the printer Embedded Web Server page to connect it to your router.
As you also have a Dell PC the simplest way will be using Windows for that purpose which provide you a lot more user friendly method to do so.
Select your Windows operating system used by your Dell PC below, then expend the Driver category and run the Full Feature Software.
Follow the steps to reconfigure wireless connection and temporary plug the USB when prompted.
After connecting the printer to your network the priner will be accessible through the network for both your PC and your Mac.