You must have "Full Access" or "Limited Access - Website" permissions to add Layout Containers.
Sign in to your site and go to the page to which you would like to add the Layout Container.
On the left-hand side, turn on Edit Mode.
Underneath the Content section of a page, click Add Layout Container.
Select the column layout of the container.
Click Create Layout Container.
The new layout container will appear at the bottom of the page. Click, drag and drop the new Layout Container anywhere on that page.