You must have "Full Access" or "Limited Access - Website" permissions to mirror Layout Containers.
If you want to have the same content on two different pages but don't want to update both when you make a change to one, you can mirror the layout container.
Mirroring a layout container allows you to display that layout container on any page that you can edit, even a page on another website. If you change the layout container, it will also change on any page it is mirrored on.
Sign in to your site and turn on Edit Mode.
Go to the page that has the Layout Container on it that you would like to mirror.
In the right-hand corner of the Layout Container, click on the gear icon.
Choose Mirror.
Click Add to My Mirrors.
Go to the page where you would like to add that mirrored Layout Container.
Underneath the Content section of a page, click Add Layout Container.
Choose Mirror Layout Container.
Choose the Layout Container that you want to mirror.