For a wireless network, you would normally use a wireless router. If you don't have a wireless router, you likely don't have a wireless network.
If you're old-fashioned like I am, and your computers each have an "etherlink" card, you can get a (pretty cheap) "ethernet bridge" and connect each computer's etherlink socket to the bridge. Instead of the bridge, you can also get an ethernet router, which is probably a more "robust" way of doing it, but is a bit more expensive.
If you have the etherlink ports on both machines, and can find a small "10/100BaseT Bridge," all Windows versions since Win98SE-SP2 let you use one of the computers as a sort of brainless network host, with what they call "Internet Connection Sharing," (ICS) and "home networking." The computer that connects to the internet (usually through a dial-up modem if you're going to use this method) should be the ICS host, and you run the network connections wizard (Start | Settings | Network Connections) and in the setup process you tell that computer what number to dial, how to log in, and tell it to share the connection. At the end of the setup, you'll be offered a chance to make a setup disk (floppy) for the other computers that are going to share the connection; and you use the floppy in any other computers you want to connect.
In order to use ICS/simplenetworking to share printers and folders, you need to also set up a "simple network" (home network) while you're running through the network setup (it may switch you to another wizard to do this). Once the "network" is set up (essentially once it's been named and the machine is told that it exists) each printer has to be "shared" on the computer it connects directly to, and a driver for that printer has to installed on each computer that will use that printer.
For purposes of sharing printers and drive folders between machines, the "simple network" uses the "names" you give to computers and printers, and really doesn't have a "host." For sharing the internet connection using the same hookup, the machine with the connection is the internet connection host, and must be the only ICS host in your setup. (My recollection is that there's a limit of 7 or 10(?) "client users" of the internet connection with this simple system.)
If you have a router, instructions should come with the router.
If one or more of your computers doesn't have a "network card" you might have to add one. (Easy for a desktop, variable difficulty/cost for a laptop.) If all your computers have at least one of the same kind of network ports the "home network" setup is pretty simple and generally sufficient for sharing drive space and printers.