Gnumeric, starting with the 1.4 series, can be run as a native application on the Microsoft Windows operating systems. On those operating systems, The Start menu should contain an entry which will launch Gnumeric. The actual location of the menu item depends on the choices made during installation.
You can also start Gnumeric from a shell window by finding the directory with the program itself which will be called gnumeric.exe. You can either move to that directory and type: