Announcements for CM actually live on a G450 or other media gateway. I dont know how you get them off AMS but to but to use announcement files in CM you need to enable the VAL(announcement board) on a G450 media gateway and then you build the announcement in CM pointing it to a wav file you load onto the G450. I use winSCP to ftp drop the files onto the G450.
To enable the announcement board on a G450, in the CM CLI enter the following. In this example I am enabling it on my number one media gateway. Board 9 is the announcement board on G450s. If you are using a different media gateway model you will need to check what slot has the announcement board
enable announcement-board 001v9
Then to build the announcement
Enter add announcement xxxx (xxxx being the extension number you are assigning to that announcement)
In the Extension field, type the extension that you want to assign to this announcement.
In the Annc Name field, type the unique name of the announcement that you are associating with the extension.
Both these videos have good info however they are from a very old version of CM so not everything will be the same