Example: I created a field with the name, "my-field", there can add it on the post, with a button "add another item" is that I want to create a list with several items, we only need to create multiple fields thus the client how they want to add.
Further explained: I created a "Text" field in the "Advanced Custom Fields" to Custom Post Type: "tariff", the field is for notes, example of how it would look on the panel:
Remarks: 1 - Note 1 | + add one more observation
Then the customer clicked on "+ add one more observation" to automatically add a new field.