Yves,
You actually do not load the voice prompts on to the A400. You must put the voice files on a PC that is running TFTP server software and configure the tenor to access the IP address of that PC as the TFTP server so that the tenor can access the voice files when needed.
Unfortunately, you will need the PC and TFTP up and running all the time or there is a possibility that the tenor would not be able to get the voice file when needed.