How to add custom fields to my wp theme?

Hi! I'm using the Aurel wp theme for my photography website. That theme has the possibility to add photo albums via backend. Unfortunately I can not add any text to such albums. I'm pretty sure these albums are added via custom post types. Has anyone hints on how I could possibly add this? What do I need to look for in the themes source code? I'm already using a child theme.

Thanks for helping!