You can move the focus to the menu bar by pressing ALT, then move around with the arrow keys, and finally open your selected menu by pressing ENTER. Or you can directly open a menu by pressing the ALT key plus the key for the underlined letter in the menu name on the menu bar.
For example, to open the File menu (File), press ALT+F.
Once a menu is open, you can select an item by moving down through the menu using the TAB or the DOWN ARROW keys. When the focus is on the command you require, press ENTER. However, the quickest way to select a command is to press the letter for that command, which is indicated by an underlined letter in the word (for example, Open, Close, New).
After you have selected a command on the menu or opened a dialog box, the insertion point in the document you are working on will return. To perform another action, you will have to go into the menu bar again using ALT or the menu shortcut.
If you accidentally press ALT, or have opened a menu and then decide you don't need to do something, you can return to your document by pressing either ALT or ESC.