POPCORN has is using slick.js for slider and models carousel. Slider is hidden by default when it does not have any post, once you publish one appears below the site header.

In order to add a slider:

Go to the WP Dashboard -> Slider -> Add Ne.

Write a title and content then use the file upload fields to upload an image or video.

You can change the Background color m font color of the content using color picker fields.