Hi Tine,

It means that your entry needs to contain at least one public domain or openly licensed cultural heritage item and you need to provide a link to the item you used in the submission form (there's a field for this 'Link to cultural heritage item(s) you used in your story') So for example, you create a story about the weather, you use this image to illustrate it https://www.europeana.eu/en/item/2020903/KMS3636 (it's CC0, so openly licensed) and you add the link https://www.europeana.eu/en/item/2020903/KMS3636 in your submission form. Hope it's more clear now, if not - please keep on asking, we're happy to help!