Networking your MAC with you shared PC printer requires a password for you MAC and a MAC driver for the printer.
Recover a lost MAC login and password: If you do not remember you MAC password then you need to recover it: I forgot my password on macbook pro: Apple Support
Install the driver for the printer. Write down the manufacturer and model. Browse to their website and download the driver. (look for downloads and/or support)
Share the printer. Here are 2 links. Skim both and see which is easier for you to follow. Mac 101: Printing (OS X Lion) Sharing a Printer, Even on a PC-Mac Home Network