The primary way to use bridges is to go to https://bridges.torproject.org/ . 
Solve the CAPTCHA there, and it will give you up to three lines, for example
(these are working):

  bridge 2.237.173.70:443
  bridge 99.192.43.230:9001

Now, you open Vidalia by double-clicking the green onion in the system tray. Go 
to Settings -> Network. Tick "My ISP blocks connections to the Tor network".
New boxes will appear below. Use the edit line and add only the IP:Port pairs.
For this example, you would first enter 2.237.173.70:443 , then press the green
"+" sign on the right. The IP will appear below in the larger box. Then, you
enter 99.192.43.230:9001 , press the green "+" sign. You can repeat this for as
many bridges as you have. Then, click OK. Now, if Tor is still/already running,
press "Stop Tor", wait, then "Start Tor" again.

If https://bridges.torproject.org/ is blocked for you, you can get bridges by 
emailing bridges@torproject.org. The rest of the process is the same. Just make
sure you don't paste in the "bridges" part of the lines in Vidalia. We are
working on a version that removes it automatically.

Hope this helps!