Use secondary featured image

Hi supporters!

Someone know how can I include a secondary featured image in the posts?
Much themes have this option, the featured image and also the secondary image, and the secondary normally is used for create a hover effect in the posts grid, etc.

I need to know how to create this module in the admin from functions.php, and also how to display this image after.

If someone can help me I will be very pleased!

Thank & best! ??