Use the keyboard to navigate the ribbon - Change focus by using the keyboard instead of a mouse

 Select the active tabof the ribbon and activate the access keys. (Alt or F10. use access keys or arrow keys to move to a different tab)

Move the focus to commands on the ribbon. (Tab or Shift + Tab )

Move the focus to each command on the ribbon forward or backward, respectively. (Tab or Shift + Tab)

Move down, up , left, or right , respectively, among the items on the ribbon (Down arrow, Uparrow, Left arrow, or Right arrow)

Expand or collapse the ribbon  (Ctrl + F1)

Display the shortcut menu for a selected item  (Shift + F10)

Move the focusto a different pane of the window such as the format picture pane, the Grammar pan, or the selection pane (F6)

Activate a selected command or control on the ribbon (Spacebar or Enter)

Open a selected menu or gallery on the ribbon  (Spacebar or Enter )

Finish modifying a value in a controlon the ribbon, and move focus back to the document (Enter)