If you have a cable modem and are unable to connect to the Internet after following all of the instructions in the manual, you may need to reset your cable modem in order for it to work.
Make sure that everything is turned on and connected correctly
Unplug the power from your cable modem
Leave it off for about five minutes
After five minutes, turn it back on and restart your router
Then go to your computer and try to connect to the Internet
If it still does not work, reset your router by holding down the reset button on the back for about 10 seconds and then try the above steps again.