Downloading the app 

To download the app, open this link from your BlackBerry: http://foursquare.com/blackberry/beta

You can also download the app from the Blackberry App World located within your device!

Updates

Foursquare for BlackBerry automatically checks for updates every 24 hours (when running) or each time you relaunch the app! Whenever a new version of the Foursquare app is available, we'll ask you if you want to upgrade. If you choose to upgrade, the latest version will download automatically and your BlackBerry should prompt you to reboot your phone. In the case that your BlackBerry does not ask you to reboot after upgrading, you should do so anyway. It's not good enough to just turn the phone off-and-on -- you must force a reboot by pressing ALT + CAPS + DELETE. This will restart the device without having to pull out the battery.

You can also download the latest version of the app by going to http://foursquare.com/blackberry/beta on your phone.