Please go to the following site for the installation instructions (all platforms) and files (Windows, macOS) for the Avaya Workplace softphone:
https://gounbc.sharepoint.com/sites/ITSSoftPhone/Shared%20Documents/Forms/AllItems.aspx
Note: The Avaya Workplace softphone client is available for Windows, macOS, Android, and iOS. On Android and iOS, the client should be downloaded from the app store.