Get a program to record your voice overs and then export it as an 16bit 44100 Hz mono wav file.
Place a copy of these new audio files in the audiobank/gloabalsounds folder. You may need to create this folder if you have not done so already.
The script refers to this location for the sound files.
--load all the global sounds here first
LoadGlobalSound("audiobank\\globalsounds\\sound1.wav",1)
subtitle[1] = "Hello there adventurer"
volume[1] = "3d" --set the volume here ("3d" = gets quieter/louder based on distance - not currently working?)
LoadGlobalSound("audiobank\\globalsounds\\sound2.wav",2)
subtitle[2] = "What? Ogres can't speak!"
volume[2] = 100
LoadGlobalSound("audiobank\\globalsounds\\sound3.wav",3)
subtitle[3] = {} --create new sub array for this sound so we can store multiple lines of subtitles
subtitle[3][1] = "What do you mean Ogres can't speak?"
subtitle[3][2] = "I'm talking right now aren't I?"
volume[3] = "3d"
LoadGlobalSound("audiobank\\globalsounds\\sound4.wav",4)
subtitle[4] = "Well I am a mighty Hero!"
volume[4] = "3d"
Add as many as you need there and change the names to your new voice over names.
Smallg has documented that script pretty well.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.