We are working on a website with The Gem theme (elementor version) and we wanted to make 2 different page templates. The second one will have a different sidebar (not the default one). 

We've  built the sidebar using the sidebar01 widget (instead of the default one).  But there is no option on edit page sections where we can asign it.

Checking guides and documentation we see that there is a configuration block: "Page Widgets" that does not appear for us. Without it we can't assign the sidebar01 as explained in this article: https://docs.codex-themes.com/article/487-types-of-sidebars

Is there a reason why we don't have it or a way to get it back?

Thanks for the responses.

I didn't realise that I didn't install the plugin at the time and it's been driving me crazy.
It took me a while to find the photo ad even though I knew what I was looking for.... I wouldn't have noticed it on my own.

Thanks, I already have the section I was missing.