How to add some pages to a custom menu sidebar widget

I have created a custom menu in the right sidebar and would like to have some but not all of my pages listed without them also being listed in the main navigation menu at the top. How do I go about doing this? I can’t quite work out how to do it.

The relevant pages are showing in the custom menu but they are still on the main menu and I don’t want that because I need them separate.

I am using the Admired theme child. My site is a members only site.

Thanks for your help