Group existing pages
Click and drag the tab of the page that you want to be the primary page so that it appears first in the list of pages that you want to group.
Hold down CTRL or SHIFT, and then click the page tabs of the pages that you want to group.
Right-click the pages that you selected, and then click Group Pages.
To separate a page group into individual pages, right-click the page tab or any of the subpage tabs, and then click Ungroup Pages.