For the sake of the beginner detail, we recommend making use of Advanced Custom Fields, which can be found at https://www.advancedcustomfields.com/
Something to note is that there is some controversy going on where their original download location at https://www.ads-software.com/plugins/advanced-custom-fields/ got taken over by a fork of Advanced Custom Fields. So the code at that specific .org URL is from the fork, and if you’re preferring the original Advanced Custom Fields, you would want to use my first link.
ACF will have plenty of documentation available on how to use it to generate all sorts of fields that you may need.