Quantum Manager replaces the standard manager in the field of type "media".
Here how the selection of article image looks like when the replacement is enabled:
You can configure in which components this replacement should be enabled. To do that proceed to Extensions > Plugins and serach for "System - Redirect Media (com_media) call to Quantum Manager".
Enable replacement of media field.
Select the components (with sections), in which replacement should be enabled. By default "Articles: Single Article".
Show or hide the image preview.
The path which will be opened by default when selecting an image (if it is not selected). By default the path of Images scope is used. You can use Quantum Manager variables here (the same as for Scopes).