When you are logged into Flow and click on the profile symbol in the top right corner, you'll see a "Download Limecraft Edge" option. Click on that:

You'll be taken to a second screen which gives you the option to download Edge for Mac or Windows. Choose whichever one you want and continue with the download.

Logging into Edge

Once you successfully downloaded Edge, you can open the application. You will get a screen asking for your license key: 

To find your license key, go to Limecraft Flow > Account Settings > Usage. There you will find your Edge licenses.