Simply place the vpk file into "Left 4 Dead 2left4dead2addons" and type "exec bindvocalizekeys" without the quotes into the console. Keys C, V, B and N will be binded to the custom radial menus.
You also can bind the keys yourself if you do not like the default configuration. Type "bind (keytobind) "+mouse_menu (menuname)" without the quotes into the console. Do this four times but change (keytobind) and (menuname). (menuname) should be custom1, custom2, custom3 and custom4.
There are 36 commands (4 radial menus with 9 commands each). Each command works with all characters. There are no character-specific commands though. This addon does not affect the two original radial menus. See pictures for command list.
This only works on local and custom servers. I don't think it works on Valve's dedicated servers. Also, please do not extensively use annoying commands like "Death Scream" or you would probably be vote-kicked. Use this addon sparingly as many players get easily annoyed by this.