Plug it in. Doesn’t matter which port – just plug the thing in.
Boot it up. I’m assuming here you have used your Pi before and know how to get into an X session.
On your desktop you’ll see an icon like this:
Double-click on it – you’ll see a new window launched entitled wpa_gui (you can also launch this by running sudo wpa_gui from the terminal). This is what it’ll look like:
Now here’s where you actually have to do something. As you’ll notice in
the image above, there is a single entry in the Adapter list – wlan0.
This is the N150 wireless dongle (unless you have other wireless
devices). If you see this, you’re OK to proceed.
Next, click on the Scan button. This will bring up a new window:
Once you have this window up and you can see your wireless network (you
might need to click scan again), double-click on it. You’ll be presented
with the following window:
Assuming you don’t want to change any settings (I use MAC filtering
rather than encryption, so it was easy enough – I’m assuming it’ll be
fairly straight-forward to set up encryption), just click on the Add
button. This will add the selected wireless network to a list you want
be able to use.
Once you’ve done this, close down this winder and the previous one until
you return to the main wpa_gui window. You’ll see you now have your
wireless network in the Network list, and looking below that you’ll see a
status of Completed (station).
And that’s pretty much it. I’ve been using it all evening without
any issue. Hopefully this’ll get you up and running as easily as it did
taken from : http://www.myraspberrypiexperience.com/