When other accounts tag you in their Stories a new button called “Add This to Your Story” appears in your Instagram DMs. Clicking the button brings you to the Instagram Stories interface where you can make any edits or simply share it to your own profile.
For privacy, users with public accounts can go to their Settings to turn off the ability for others to reshare their posts.
This is great for businesses that use Instagram Story Highlights to share customer reviews. Rather than having to screenshot a review and create a new story, you can use the repost feature to quickly share new reviews on your highlights.