Insert a new element and choose Tabbed Content from the Element Gallery.
You will see the following error. Ignore it and click the Gear.
Enter the titles of your tabs, then click "Save."
Insert a new element (you should use the Text Block).
Define your Formatted Text Block.
Do the same process for any remaining tabs you have created.
Then submit changes and view as published to see the results.
Your tabs will appear as follows: