When you want to edit the advanced custom fields for a WordPress blogpost, you must first install the ACF to REST API plugin.
For sending authenticated POST request I used the JWT Autentication for WP-API plugin.
Now I have created a blogpost in WordPress and filled the advanced custom field: “my-field-1” with value: “value 1”.
The blogpost Id = 15.
To update the value, I used the following code: