Within Teamwork Chat, you can download the desktop version from the Teamwork website.
The desktop app is available for both Windows and Mac OS.
On the chat apps section of the website, click the download button under Windows:
Once the download is complete, run the installer and follow the steps.
Mac OS X
On the chat apps section of the website, click the download button under Mac:
Once the download is complete, double click the ZIP archive to extract the contents. Then double click the Teamwork Chat application (which was extracted from the ZIP) to launch it.
Note: It is recommend to move the app to your Applications folder.
For more information, see: Updating the Teamwork Chat Desktop App