For concrete5 version 8 with the Elemental theme and version 9 with the Atomik theme, you will likely want to edit the Global Settings to:

• Preserve any theme grid box about individual tab elements: Remove
• Classes that will be removed from elements contained within tabs: container
• Wrap entire tab set in any theme grid box: Wrap

Full documentation at https://c5magic.co.uk/addons/magic-tabs