Are you talking about this https://www.advancedcustomfields.com/resources/adding-custom-settings-fields/
ACF will not automatically add any custom settings that you create to anything. You need to create other filters to alter the way the field behaves. For example, if you want to somehow use the new setting on the front end then you’d create an acf/format_value filter https://www.advancedcustomfields.com/resources/acf-format_value/
