This can be done from the portal fairly easily, although Google have thrown a bit of a spanner in the works with their recent update which stops us adding a Flash exception for the portal!
You can still do it in Chrome, but you can't listen back to the files.
Alternatively you can make all the changes in Firefox or Internet Explorer, or upload the files in Chrome and call the number to listen to the audio.
Load a browser and log in to the portal.
Go to 'Configuration' and then 'service accounts'.
Click 'configure' to the right of the 'Main' account.
Click the 'IVR Menus' tab.
At the bottom left of the screen, to the right of the 'Top Level' entry, click the blue folder icon.
A new window will open.
On the left, expand the 'menu prompt' section - this is where the greeting and menu options audio file needs to be uploaded. It needs to be a WAV 5mb or under.
You may get a flash permissions box, if you do, select 'allow'.
Change the 'file options' box from 'record' to 'upload'.
Click 'Choose file', select the file and click OK.
The number options can be adjusted to the right, the 'timeout' option is where it will go if the don't pick an option.
Click 'save changes' at the bottom.