Fairly easy with a bit of patience. Some questions though.
What operating systems on the PCs and how do you connect to internet - Cable phone broadband or dial up?
Do you want to use PCs independently to access the internet or use the internet connection of one PC?
Do you want to connect PCs by wire or use wireless?
Most flexible option for the PCs is to buy a network hub/router. Type depends on broadband connection cable or telephone line. Needs network ports on both PCs but on most modern (ish) PCs this is built in.
HAve alook at click here for a general tutorial. May answer some questions you have.
Do you already have a printer you want to use. Would you mind having this connected to one PC which must be switched on whenever you want to use the printer. Option is a printer with built in network capability or a print server. Both ad to costs but network printers are available for less than £100.