Sticky Single Side Bar Item

Hello, I am following this guide here to sticky a side bar
https://www.squarewebsites.org/squarespace-plugins/lazy-summaries?peachs_apc=tuan-phan

But the issue is I don't want the WHOLE bar stickyed, just one table of contents bar - attached is a image of the side bar and blog post, i put a arrow towards the one i simply want stickied. I was it to sticky to the top after scrolling far enough down to get past the rest of the bar

Can you share link to this page? We can check easier