In Questions & Answers configuration page, you can choose to enable Questions & Answers app for all of your Confluence spaces or selected spaces or disable for some spaces.
To go to this page, login to Confluence space as an administrator, go to Settings page of Confluence. On the left sidebar, click on Questions & Answers. The Questions & Answers configuration page will be opened:
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In this page, you have 3 options to choose.
+ all spaces: Enable Questions & Answers app for all of your spaces. Users can use Questions & Answers app from all spaces.
+ only these spaces: Enable Questions & Answers for only selected spaces. Other spaces cannot use this app.
+ except these spaces: Questions & Answers app will be disabled for these spaces and enabled for other spaces.
Click Save to save your configuration.