How to add a featured image for each unit?

I’m currently trying to add an image for each unit. I’d like this image to show up when I use the [wpcourse course="1" module="4" module_desc="true" /] shortcode.

I’m currently displaying all the units on this page: https://trainingstage.ifipartners.org/

Is there a way to add a “Featured image” to each unit and have it show up when using the shortcode above?

https://wordpress.org/plugins/easy-digital-downloads-addon-for-wp-courseware/