OK, here is a step by step. This assumes you have Leafpad text editor installed, I know VI isnt for everyone.

1. Open the X Terminal
2. Gain root access
3. Use Leafpad to edit the config file
leafpad /opt/barriosquare/barrioConfig.py
4. Change the following line (remove "play")
AUTHORIZATION_EXCHANGE_URL = 'http://api.playfoursquare.com/v1/authexchange'
To
AUTHORIZATION_EXCHANGE_URL = 'http://api.foursquare.com/v1/authexchange'
5. Save the file with Leafpad and exit
6. Now run Barriosquare from the menu

Does that all make sense?
Only new to the forums here so not sure of the level of Linux knowledge most people have.
Let me know if you run in to any problems, happy to help ^_^