After some digging around on the internet and finding nothing of any real help, decided to experiment on site - discovered solution by accident.
1) Create a new article (the content that will be tied to the new menu button). For me, this was going to an existing article, saving it as a copy and editing the copy - then changing the Title to what I wanted.
2) Similar to step 1, I went to menus, opened an existing menu item, saved as copy. Then I changed the Title, changed the article it was linked to, saved.
When I swapped tabs back to the wep-page and reloaded it (ctrl+f5), new menu button appeared...along with the link to take it to the new page. DONE