I think there may be some language problem here.

The way both Word and various other program (like Internet Explorer) work is
that they normally run only one instance of thr application, but that
instance can have multiple windows open. The multiple windows are each main
windows and so look kine multiple instances in the taskbar at the bottom.

I don't know the details of how this is done in VC, but you might look up
"SDI" (Single Document Interface)