To receive a free sample from Diptyque Perfume via Facebook ads, first follow and interact with their page by liking posts or commenting on them. Return after stepping away briefly; you should then see the promotion in your feed labeled as an advertisement where it will ask for basic personal details like name, address, and email to apply. If this doesn't happen immediately, check that ad preferences are set correctly within Facebook settings or interact more with their content regularly since appearances can vary based on engagement levels.