To add tags to a Custom Post Type (CPT) and manage them, you have two different paths depending on what you mean by “post by ACF”:

• Path A: You want to add standard WordPress Tags (or a custom taxonomy) to your CPT so they show up in the admin sidebar.
• Path B: You are using an ACF Front-end Form (acf_form()) and want users to be able to assign tags when submitting a post from the front-end.

Here is how to handle both scenarios.

Path A: Registering Tags for your CPT (Admin Backend)

If you just need the default WordPress “Tags” UI box to appear on your custom post type editing screen, you need to update your CPT registration code.

1. Using Built-in WordPress Tags

Look for your register_post_type function inside your theme’s functions.php file (or wherever you registered the CPT) and add 'post_tag' to the taxonomies array: