You need to identify which part of Article 3.2 applies. Does the good comply with (a) - wholly obtained, known as WO or (b) - produced entirely, known in ChAFTA as WP which means Wholly Produced or (c) the good complies with a PSR? You then need to gather the supporting evidence that shows the good is originating. This evidence is the same as would have been sent to an authorised body for a COO.
Information on how to apply for an 'Advance Ruling' is availableon the Department of Foreign Affairs and Trade website.