The Ethernet Switch
Switches and wireless access points are available from Micro Plus.
Locate the broadband power supply connector box. Most are black boxes, as shown on the left. They have 3 connections - the power cable, the wire to the outside antenna (marked OUT or POE) and the wire to your computer (marked IN or LAN).
Turn off your computer, and follow the wire from the broadband connector box to the computer. You need to unplug this - but be aware that it doesn't just pull out - there is a little plastic nib on the side that you need to squeeze to release it. Have a look at the new cable - you should be able to see the nib clearly (and it will probably be a lot easier to see than the back of your computer, if it's anything like mine!).
Plug the Ethernet cable you bought into the computer exactly where the other one came from. You should now have 2 cable ends - the other end of the new one and the old one you just unplugged. They go into the switch (see right - it doesn't matter which one goes where, but I like to put the cable to the broadband box in number 1). Also plug cables in for any other devices you want to connect, and plug the other ends into the devices. Finally, plug the power supply into the switch, plug the other end into your mains socket and turn it on.
Now start up your computer again, and check you can still access the Internet. Then try the other devices.