How to publish Showcase in a theme

First Copy the Showcase id from Product Showcase :

1-> Click on the Showcase from the left sidebar
2-> Then copy the Showcase id

After that add a showcase in section or block on the Page

1-> Select a page
2-> Add a block or section
3-> Click on Apps
4-> Select Product Showcase

Then paste the Showcase id of theme block or theme section :

1-> Paste Showcase id theme block or theme section
2-> Finally click on the Save button

Setup Guide