Which Pages are External Page Links?
After logging into the CMS Select editor, you would click on 'Pages' at the top. Pages with an 'arrow' on the right side are external links, as show below:
How do I change External Page Links to HTTPs?
If you click on that External Page Link a menu will display with the link being used and you can edit the link by changing http:// to https://
Then you can use the back arrow to update any other External Page Links, before selecting Publish in the upper right.
Your pages may have links in the content that need to be updated as well or buttons on the pages. While updating the 'Pages' for the primary navigation will help, take a moment to review your pages for any links or buttons that also may need to be changed. This article explains how to change links in the Text widget.