voicemail greetings

I have a customer that sent me their voicemail greeting. I know I need to change it to wav 8/16. But once I do that where do I upload it? I have clicked around and cant seem to find an option to upload vm's extension greetings. I do see a place in the voicemail section that has an options...

I want to change the default voicemail greeting globally for all domains. Currently the default intro is something like ......"the person at extension 1000 is not available, record your message after the tone, ..... Is there a simple way to replace this default message with another wave fiel...

I would like to limit my users to only one possible recorded voicemail greeting. Doing this user by user would be ideal but at the global level would be fine, too. If anyone knows how to do this, I'm all ears, I haven't found anything in the docs or here on the forum. Thanks!