Adding scrollbar

I have this site, build using Sphinx, and I want to create a scrollbar into the sidebar. Any suggestion?

height: 100vh; overflow: auto; on the sidebar container. You set it to the height of the viewport, then tell it to overflow if needed.

There is no sidebar content, Have used Sphinx before>?

I assumed that was a screenshot of what you’d generated?

No, planning to do similar to it.