How can I download flash player on the kindle fire
Android (Google) dropped all support for Flash last summer. The reason is the same one Apple gave seven years ago when they released iOS: Playing Flash content is very processor consumptive and it kills batteries... as well as shortening the battery life in mobile devices.
Android recommends using either "Dolphin" or Puffin" as your browser (BOTH are free in the GooglePlay store). They use "server side rendering" of Flash content to reduce the load on your Android device.