Yes, you can. In the "Ads" section navigate to the "Existing posts":
There, you’ll see a list of available posts for Facebook and Instagram:
You can:
Preview each ad
Check engagement metrics
Filter by type (available for promotion, ad post, scheduled, or published)
You can choose either Facebook or Instagram posts - but not both in the same campaign.
Note: For Instagram, only image and carousel posts can be used as existing posts for ads. Video posts cannot be used, as they are not processed via Meta API.
Another option is to enter post IDs in bulk, just separate them with commas or spaces:
Keep in mind: you can't use existing posts and creative sets together in the same ad. Read more about Bulk Creation here.