The keyboard can be used to access the menu bar when you hold down the <Alt> key and simultaneously press the underscored character of the menu button of interest. For example, press <Alt><T> to pull down the Tools menu.
Once the menu system has the focus, use the cursor keys to change menu buttons (<Left>, <Right>),
or change menu items (<Up>, <Down>).
Pressing <Right> on a menu item that has a submenu will open the submenu.
Press <Enter> on a selected menu item to execute that action.
Many menu items have access keys and quick keys associated with them. An access key is shown by the underscored letter in the menu item name, for example the "D" of Diagnostics.
With the Mesh menu open, pressing <d> on the keyboard has the same effect as navigating to that menu item with the cursor keys and then pressing <Enter>, in this case opening the Mesh Diagnostics dialog.
A quick key (if one is assigned) is displayed to the right of the menu item, such as this one for Step in the Solution menu.
The quick key can be used to activate that menu item directly, even if the menu system does not have the focus.