It is impossible to access certain menus / toolbars / buttons without the mouse.
Add a key to trigger a keyboard accelerator (see https://msdn.microsoft.com/en-us/library/windows/desktop/ms646337(v=vs.85).aspx for full description)
When the user presses the key (e.g. ALT) the relevant menu or button gets an underline to denote the trigger for it, e.g. to access page settings one could press ALT + P.
Add a general key shortcut to access the menu, typically on several operating systems this is keyboard key F10, for most (all ?) applications in it.
Note that this is distinct from the "normal" keyboard shortcuts. Accelerators tend to be context dependent and can trigger in any dialog or interface that has options or buttons.