Pretty nice summation by Ragtop, there.
Depending on your physical situation will depend on whether wired or wirelss would be more practical. For instance, if all PC's are to be in the same room, then wired is easy and fine - just get a router, NIC's for each PC and some patch cables. But if you are in a rented apartment or something, and all PC are in different rooms, running cables between rooms could be messy / dangerous; then wireless would be the way to go. You'd need a wireless router and wireless NIC's for each PC.
Need any more help, just ask - someone here will know!
Cheers
Mick
Oh, and Welcome to TechIMO!!