Using Sidebar With Theme That Does Not Have A Sidebar

I was hoping to use this to create a sidebar within a theme that does not have any sidebars currently (https://www.competethemes.com/chosen-live-demo/).

After adding a sidebar using the plugin, I am unable to set it as the “default” sidebar, screenshot: https://puu.sh/pebIa/5b42106dc5.png

Do I need to create a custom child theme sidebar as you mentioned in Other Notes:

“Some themes register different sidebars for their page templates, which means there isn’t a default sidebar that can be replaced. To use Simple Page Sidebars in this instance, you can create a child theme and force page templates with custom sidebars to use the default sidebar.”

Thanks so much!

https://www.ads-software.com/plugins/simple-page-sidebars/