Yes, you can. In the Creatives section navigate to the Existing posts.
Here you can select posts from the list:
Here you can see an ad preview, engagement metrics for each published post and post filtering (all available for promotion/ad post/scheduled/published)
Note: you can either choose post for Facebook or for Instagram. It's not possible to use both Facebook and Instagram posts in the same campaign.
Another option is to enter post IDs in bulk, separate them commas or spaces:
You cannot use existing posts and creative sets at the same time. Read more about Bulk Creation here.