To activate VK stories, you must:
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1) Go to the Accounts section
2) Select the VK page (connect the VK page)
3) On the right in the list, click on the circle, give access rights. The activated page will be marked with a green circle with a check mark.

To publish a VK story, you need to go to the Posts - Schedule a post section.
Select a page, upload a photo or video and click on the checkbox Post to Stories (Vkontakte)