Hello.... what is the make and model of the printer?
What OS are you trying to install it on?
If you have the Driver Disc that came along with the printer, I would suggest running it on the PC and going through the whole setup process. During the installation process the program will ask you to connect the printer and switch it on, do that and the PC will automatically install the drivers and the software for the Printer on your machine.
In addition to alyoska's instructions, if you do not have the Printer Installation CD, Go to the Printer Vendor site. and download the drivers for the OS (Windows 7, I assume) since you posted in this forum.