Extract contents of zip file(s) to cities\diskcache\voices
Select suitable voice inside program settings too, of course
If the voice is not working check the following:
First check to ensure that you have a voice selected. To do this, when in Maps, click on Spanner>Navigation>Drive Guidance. You will now see a list of voices. The ones with a little phone icon to the left are the ones already installed on your phone. Make sure you have one of them selected. Note there is a different voice setting for drive and walk.
Second thing to check is the navigation volume. After you start navigation, use the the volume up toggle.