Hi Archana,
You can add stories ads to your Facebook campaigns by following the steps below:
In Ads Manager, you can use Automatic placements or Edit placement and ensure that Instagram Stories is selected to get the most efficient delivery. Facebook will deliver ad content in the placement believed most likely to help drive campaign results and use your budget efficiently based on your optimization goal. When you select Instagram Stories ads as a placement, your existing creative will be automatically transformed into a native Stories ad. Or you can upload content created specifically for Stories.
That’s it. hope this helps 🙂