1. Tap the pencil icon to enter the Storyboard view for your story.
2. Tap the down arrow to expand the Sharing panel.
4. Tap the toggle next to "Allow Viewers to Duplicate Story" so that it turns green and then tap "Done".
If the person you shared your story with cannot see the option to copy your story after you change your settings, instruct them to drag their finger down on the Stories screen in order to refresh.