From the actions list on the right side of the environment's Details page, click Edit Environment > Customize Viewer.
The Customize Environment Viewer page is displayed.
To change the basic settings, from the Apply settings from dropdown, select Custom Settings.
The basic settings are now editable.
To access advanced settings, click Switch to Advanced Mode.
When you're done making changes, click Save. Your customizations will be stored with the environment.
If your environment was created from a blueprint, you can apply your customizations to the snapshot from which it was created.
To do that, at the top of the page, activate the Apply viewer settings to snapshot checkbox and then click Save.
Keep in mind that applying changes to the snapshot will affect all currently active environments, as well as any environments that are created from that snapshot in the future.