1. Buy a crossover cat5 cable. Be careful not regular cat 5 cable. Connect both computers with their network adaptor card (some people call it ethernet card, or NIC)
They have a jack looks like a telephone jack but has eight wires (telephone jack has four wires)
2. Buy a switch and two cat5 regular cable. Connect both computers to the switch with cable.
3. If you also want share internet (broadband such as DSL or calbe) connection, buy a router/switch and two cat5 regular cable.
There is a very good website:
www.homenethelp.com
You can find a lot of tutorials, and also a forum you can ask questions.
Enjoy networking!