To access the Space configuration of Hangouts Chat for Confluence, click on the “Spaces” dropdown next to the Confluence logo in the upper-right-hand corner and select “Space directory”.
Here, click on the circled (i) button to access the Space details page of the Space you want to setup notifications for.
For newer versions of Confluence, you now need to select the “Add-ons” tab on the top of the page. In older versions of Confluence, this tab is called “Space Admin”. Underneath, select the “Hangouts Chat for Confluence” tab.
Here, you can again setup Hangouts Chat rooms and users to be notified of any updates that are checked under the “When to show notifications” section.