Sorry, Firefox isn't made for ChromeOS used on the Chromebook.

I downloaded the app, but when i go to open it it says "this file type is not supported, open the Chrome Web Store to find an app that can open this type of file" and I don't even know where to start looking for it if there is one. REALLY NEED HELP !! please!

Oh ok thats why the darn thing wont work. Ok thank you !

Never say never.

It is posible to dual boot chromebooks and that opens up the possibilities like adding a complete lighweight Linux distro including Firefox.

I also note running chromebooks in developer mode gives access to the built in Linux quite possibly Firefox would be installable on that. I also note it seems possible to run wine and in turn Windows programs including Firefox.

Any of that is a lot of trouble to attempt & not what most chromebook users would try. Chromebooks tend not to be bought by those intending to use it as a Linux machine.

A couple of articles that may be of interest if you wish to try to force a chromebook to use Firefox

• Chromestory: How do I Install Software / Programs on My Chromebook?
  http://www.chromestory.com/2013/06/how-do-i-install-software-programs-on-my-chromebook/
• HowToGeek: How to Run Windows Software on a Chromebook
  http://www.howtogeek.com/173353/how-to-run-windows-software-on-a-chromebook/
  • http://www.howtogeek.com/162120/how-to-install-ubuntu-linux-on-your-chromebook-with-crouton/
    How to Install Ubuntu Linux on Your Chromebook with Crouton

It depends on the hardware of said Chromebook on whether you can install a Linux distro. It will be slower also.

Chromebook uses Chrome as the OS. https://en.wikipedia.org/wiki/Chrome_OS