All pages in a c5 site are under the home page. It will be tricky to have a drop down menu under "Home" with some pages but not others. You should either create another top-level page to be the parent of subpages 1, 2, and 3 (call it something generic like "Info" maybe?), and that will be a sibling of About and Contact. Or creat a dummy page called "Home" under the real home page, and put subpages 1, 2, and 3 under that (and then exclude the real home page from the menu).