A case can only be created from within a collection.
1) Click on “+ New case” on the top right of the page.
2) Choose a name for your case and press “Create”
3) Select the slides which you want to add to your case.
4) Click on “>” button
The slides now have been added to your case. To view your cases, go back to the list by using the “Back to cases” button, or preview your newly created case by clicking on “Preview” button.