How to edit the post content & post title

To edit post content, you need to add a new field and then select it under Editing > Post title or Editing > Post content in the form settings. When configured this way, the value from the chosen ACF field will be saved in the designed core post field when a form is submitted.

Note, as these fields generally don't need to appear in the admin view for a field group, you may choose to hide the fields in the admin.