The order that the page links or buttons appear is managed from the display order from the My Websites -> Main -> Customise Design -> Navigation Menu -> Manage Nav Items
The display order is changed by editing the display order value displaying pages in numerical order. The smaller the number the earlier the link will be displayed in the navigation menu; to the left on a horizontal menu or higher up in a vertical menu. It does not matter which numbers are used it just goes from 1 to 9999.
You can also enable a Dropdown navigation.