A switch is a device that allows multiple computers to connect to one Internet connection. Unlike a network hub, which serves a similar purpose, a switch has the ability to manage the traffic that passes through it. A switch can be a stand-alone device, suitable for home or small office use, or rack-mounted for larger network applications. Switches also vary widely in traffic management capability. It's important to clearly define your requirements before you purchase a switch so you can buy the one best suited to your needs.
Connect your modem to your Internet input line. Whether it is DSL, cable or satellite, your modem is the device that brings the signal into your network.
Connect one end of an Ethernet cable to your modem. This will most likely be a Cat 5 or Cat 6 Ethernet cable. Connect the other end to your switch. Although not required, it's a good idea to connect this end to Slot 1 on your switch so you can quickly differentiate between incoming and outgoing cables.
Connect one end of another Ethernet cable to a different slot on your switch. Connect the other end of this cable to the Ethernet slot on a computer you wish to connect to the Internet.
Repeat Step 3 for all computers you wish to connect.