First, give your story a title and brief description. Descriptions shouldn't be very long, just a taster of what your story is about. Don't worry, you can always edit them later.
From How to make a story with Yarn by Dean Vipond

First added by Rosie Wilkinson

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How can I add my own content to Yarn?

A few pointers on using free web platforms from which to add your own photos, video and audio files...