Stick the sidebar of table of content (TOC) in the distill template.

Hello! This is really an amazing template but I have one thing that I want to figure out. I have just successfully activated the sidebar on the distill template, however, it sticks to the top of the page and when I scroll down the table is not shown on the left as in the post template. I really want to know how to stick it to be kept shown on the left as I have a very long article, thanks a lot!