Telling IIS to serve up a file as a download

I created a virtual directory in IIS.
I put the file that I wanted others to download in it. In this case an *.apk file.
I turned on directory browsing.
I clicked on the file and got a 404 error.

I added the mime type *.apk, application\android to Mime-types in IIS.
I clicked on the file and it downloaded.