Follow the instructions and install GNUWin. You should pay attention to the directory where your application is being installed. (You will need it later1)
Follow these instructions and add make to your environment variables. As I told you before, now it is time to know where your application was installed.
FYI: The default directory is C:\Program Files (x86)\GnuWin32\.
Now, update the PATH to include the bin directory of the newly installed program.
A typical example of what one might add to the path is: ...;C:\Program Files (x86)\GnuWin32\bin