For the computer voice you only download the corresponding .CAB file in our voice section and unpack it to folder on your PC.
Preferable name the folder "LoquendoTTS" ;)
Now you copy the content from the LoquendoTTS folder on your device into the folder on your PC - overwriting existing files.
This step is to make sure the patched files overwriting the standard files provided by TT, so don't mess it up ;)
When done copy the folder back to your device.
If you are good with the Explorer and know what you do:
Simply copy the .cab content directly into the LoquendoTTS folder on your device, but DO NOT overwrite existing files.
You can delete the chinese files as they are only for the Asian support of keyboard and map.