How can I add a section without adding it to the menu?

To resolve this issue, you can refer our answer in the following question:
http://www.designwall.com/question/is-it-possible-to-display-a-page-on-the-main-onepage-without-it-being-linked-in-the-main-menu/
Also, you can add the following code to the style.css file to hide the menu item. However, you need change the “home” word with menu title that you want to remove.

.navbar .nav > li > a[href="#home"] {
    display: none;
}

With all good wishes for a brilliant and happy Christmas season. Hope things are going all right with you 😀
Hope this helps !