Link re-direction in the wordpress page menus

On my blog, https://hannahmontanazone.com/ I would like to make it so when someone clicks one of the links at the top, for example gallery, they get re-directed to a different page (not WordPress page).

Temporarily I’ve added my own link in there by playing with the index.php of my theme but as you can see it doesn’t quite fit in and I don’t know how to change its style.