Group your opted-in subscribers to target them with Marketing Messages.
Select the Ad Account where this audience will be saved.
Give this audience a clear name (e.g., "Promo 6.6 Subscribers").
This audience will be automatically populated using the PSIDs (Page-Scoped IDs) of users who have actively opted-in to receive messages from your connected Page. Meta requires this data to be mapped using the `PAGEUID` schema.