Mosaic needs to be activated in the Add-on control panel. To activate Mosaic:
- Near the bottom of the Toolbar, click on your User Name, then select Site Setup.
- In the General Section, click Add-ons.
- In the Available add-ons section, find Mosaic, then click the adjacent Install button.

- If successful, Mosaic will appear under the Activated add-ons section.

Once Plone Mosaic is installed and activated, the Plone site should still look and behave normally. However, we now have access to Mosaic's layout editor.