It’s possible to target people who have viewed any video upload from your Facebook and Instagram profiles, without them needing to have “Liked” or “Followed” your Facebook and Instagram profiles.
To get started, confirm that you have Page Advertiser access or Page Admin access to the Facebook Page of the brand.
Verify that the brand has synced the Instagram Business Profile of the Instagram Account to the Facebook Page. Note: This is only required if you’d like to target video uploads from your Instagram Business Profile.
Next, in the Audiences section of Facebook Ads Manager, create a custom audience made of fans who have interacted with the Instagram Business Profile of the brand. You can do this by clicking on “Create Audience,” followed by “Video," followed by selecting the videos from which you'd like to target fans. We recommend using three second video views and a length of 365 days:
Finally, import that custom audience into the service by pressing “Add New,” “Facebook,” “Facebook Custom Audience,” followed by selecting the audience name in the “Template Options” section: