For that positioning, you can either add it after the members tab or extra tabs: end section. I usually choose the latter:
That last line is what you'll add to make the tab. You can give it a custom CSS class like "myNewTab", as I exampled, or keep it something familiar like "home" to copy that styling. Change the "someHref" to the href, and the "someNewPhrase" to a new phrase that you can create in the Phrases section of Appearance.
EDIT: If it's a node that you want to add as a tab, there's an add-on called "Nodes as Tabs" that will let you make navTabs from nodes.