Connect to a wireless network
If you have a wireless-enabled computer,
you can connect to a wireless network that is within range to get
access to the internet, view shared files on the network, and so on.
If you have a wireless hardware switch on your computer, make sure
that it is turned on.
Click the network menu in the menu bar, and click the name of the
network you want to connect to. If the name of the network isn't in the list, select More Networks to
see if the network is further down the list. If you still don't see
the network, you may be out of range or the network might be hidden.
If the network is protected by a password (encryption key), enter the
password when prompted and click Connect. If you do not know the key, it may be written on the underside of the wireless router or base station, in its instruction manual, or you may have to ask the person who administers the wireless network.
The network icon will change appearance as the computer attempts to
connect to the network.
If the connection is successful, the icon will change to a dot with
several bars above it. More bars indicate a stronger connection to the
network. If there aren't many bars, the connection is weak and might
not be very reliable.
If the connection is not successful, you may be asked for your
password again or it might just tell you that the connection has been
disconnected. There are a number of things that could have caused this
to happen. You could have entered the wrong password, the wireless
signal could be too weak, or your computer's wireless card might have
a problem, for example. See Wireless network troubleshooter for more
A stronger connection to a wireless network does not necessarily mean
that you have a faster internet connection, or that you will have
faster download speeds. The wireless connection connects your computer
to the device which provides the internet connection (like a router or
modem), but the two connections are actually different, and so will
run at different speeds.
From: Ubuntu Documentation