Can't setting up ToC whit Ease Theme

Developer help
1

I’m trying to add TOC for my blog and followed this link so far：
Tutorial: How to add a table of contents to your Ghost site

However I can not achieve Scrollable TOC on the side of the post as shown on " Advanced styling " on the above guide. And I was only able to add the TOC on the top of the blog post.

Is it because I am using the Ease Theme?

Thank You~