Warzone can be played for free on the website, https://www.warzone.com, or via the iOS or Android app.
However, it's also available as a downloadable native app for Windows, Mac, and Linux. This is called the standalone client. It is only available for members. Links to download are below.
 Download Links
 Installation Instructions
- Click the Windows download link above.
- Once it finishes downloading, open it from your browser's Downloads.
- Click "Extract all".
- Give it a folder to extract to, such as to your Desktop.
- Go to the folder you extracted it to and double-click on Warzone.
Same steps as Windows, except click on the Linux download link instead of a Windows download link.
(help out by providing instructions here!)