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To do this, tap your profile photo (it'll say "Your Story" below it) at the top-left corner of the screen. This plays the first clip of your story. If anybody has viewed your story, you'll see the icon of an eye with a number next to it at the bottom of your screen. Tap on it to see the list of followers who have viewed your photo.  If you have posted multiple photos or clips to your story, you can also swipe left and right on their thumbnails at the top of the screen to see who has viewed each individual photo. Tap the X in the top-right corner of the screen once you are finished reviewing your story viewers. Although stories disappear after 24 hours, you can select certain content to remain visible on your profile using Highlights. People can view your highlights at any time by tapping them at the top of your profile. Here's how:  Tap the heart at the bottom of your story to open the Add to Highlights menu. Tap an existing Highlights album, or tap + to create a new one. If you're creating a new album, you can give it a name and choose a cover image. Once you've created Highlights, you can manage them on your profile.

Summary:
Open your story. Swipe up to see who has viewed your story. Add a story post to your Highlights.