Instagram Story Publishing

First, open up the compose tab as you normally would when creating a post and select your Instagram account from the drop-down list. In the top-left corner of the text area of the compose tab, you should see a dropdown option where you can pick the type of post you would like to compose:

From here you can choose Instagram Story and upload your video file using paperclip icon in the bottom right corner of the text box.

On the window that appears, upload your image or video in the same way you normally would attach media to your post, from whichever source you have available:

Once uploaded, your Story media should appear in the "Attachments" section of the composer:

Thats it! Once you're happy with your Story, either schedule it for the future or publish it straight away and it should look something like this: