Firefox's default behavior is to display top sites on the New Tab page. Learn how to customize this page by pinning, removing sites or rearranging these sites.
Click the pin icon in the top-left corner of the Tile to lock it in that position on the page.
Click the "X" in the top-right corner of the site to delete it from the page.
Click and drag a Tile into the position you want. It will be "pinned" to its new location.
You can also open the bookmarks library and drag bookmarks to the New Tab page.