Most wireless routers will have at least four ethernet ports..
These will look a bit like
You will need your PC to have one as well (most recent ones do), but if it doesn't, you can buy an ethernet card (
http://www.ebuyer.com/product/118964 ), and the correct length of Cat 5, 5e or 6 Ethernet cable..
You will also need a router (assuming you don't have one, but if you have a wireless network, you probably do as the Ambit modem does not do wireless).
http://www.ebuyer.com/product/35433 may be a good router, but Virgin also do their own branded netgear which is a bit more expensive, but they will help you set it up.