Edit or add links to Top Menu nav

I would like to add a "register" link to the top menu bar, with an icon similar to that of the other two pre-defined links. How can I do that?

I tried to add it via the menu option, but any link I add automatically appears before the pre-defined links. I want it to show after. May I please know how can that be done?

--can do the coding myself, I just need to know where it is. : )