Purchase a WiFi
dongle and make sure that it is compatible with the Pi using this list of compatible
products.
Connect the
adapter into one of the Pi's USB slots. Boot up the Pi, login to the pi and go
to the Pi's GUI. Navigate to the Pi's start menu on the top left corner of the
GUI. Select the application settings and then click on the WiFi configuration
program. With your internet ssid and password handy you should first press the
scan button then select and double click your network as it comes up. You will
be prompted to enter in your password, after you have done this you can click
connect. The WiFi application should then set up the connection and tell you in
the status bar that the internet is connected.
If this doesn't
work or your ssid isn't coming up your WiFi adapter possibly has some compatibility
issues with the Pi. To solve these problems it is a good idea to look up your adapter
on the Raspberry Pi's list of compatible accessories and then follow the links
to the find the available drivers for your adapter.