Customize → Single
This is single post eg :Single Demo in here you can setting layout of this page
So when you in the Customize then you should click to post detail
Click the Blog single.
1 → Sidebar Layout
You can use a separate sidebar for the single page , when enable Use Single sidebar
2 → Social Share
You can use button share fixed or below the post
3 → Videos Box
Disable or Enable New Video
4 → Read More Box
Disable or Enable Read More Box
5 → Facebook Comments
if you want to get notification when some one comment to your fanpage to enter APP IP
You can get APP IP here :https://developers.facebook.com/apps/