Hello @buxton161
I hope you’re doing well today!
Where you can place your custom sidebars depends solely on the theme. Most themes provide widget areas on the sides and/or in footer. Custom Sidebars plugin can only replace those sidebars that are already registered in the theme.
That could as well be somewhere inside or around header, provided that the theme does call out sidebar there.
If your theme doesn’t do this, consider creating a child theme. In such child theme you could register new sidebar and then call it in your header template file.
Here’s more information about child themes:
https://developer.ww.wp.xz.cn/themes/advanced-topics/child-themes/
and about adding sidebars to theme
https://codex.ww.wp.xz.cn/Sidebars
With such (child) theme that displays sidebar in header area, plugin will also be able to add custom sidebars there just like in any other location that it already can handle on your site.
Best regards,
Adam
