Press Control+w, then hit q to close each window at a time.
Update: Also consider eckes answer which may be more useful to you, involving :on (read below) if you don’t want to do it one window at a time.
Press Control+w, then hit q to close each window at a time.
Update: Also consider eckes answer which may be more useful to you, involving :on (read below) if you don’t want to do it one window at a time.