OSX machines require a provisioning file be installed on the device. A Foxpass administrator can create this file by visiting this page and creating one for the Foxpass-enabled SSIDs in your organization.
Click the 'Download Config' button:
WiFi Networks config page
Then click on the .mobileconfig file to install it.
Adding the config
You can optionally save your Foxpass username and password to your system's keychain. This will prevent you from having to re-enter it every time you connect to the network.
Optional Wi-Fi config
OSX will then prompt you to enter your system password in order to save the changes. Just connect to the Wi-Fi network and you're good to go!