You can use the Resource Groups page to edit the description of a Resource Group resource for the target Azure platform.
In the Web Interface toolbar, select the Platforms tab.
Select the platform, then click Edit.
Under Associations, select the Resource Groups tab, then click Edit (or double-click the resource group) to open the Edit Resource group dialog.
Modify the Description for the Resource Group resource.
Click Save to update the Resource Group resource.
Click Close to exit the dialog.