With page post ads you can promote the content you have on your Facebook page. You will be able to promote both your published and unpublished page posts.
Select if you want to select a specific page post or if you want to search for the page post by Page post id. Since your posts are already created you will not be able to modify them, only select the post(s) you want to promote.
Select where on Facebook you want your Page Post ad to be shown.
Click on “Create” in order to generate your page post ad.
Once you have generated the page post ad you are ready for the next step. Go to “Set Targeting” to set up your targeting for the generated creatives.