Go to Google Input Tools on Windows page, check the Hindi box from the right, select the I agree to the Google Terms of Service and Privacy Policy option and click the Download button. Install the utility and click the EN button from the Windows taskbar. Select HI Hindi (India) option and you will be able to type in Hindi. Also, if you want, you can change Facebook language. Go to Settings > General, select Hindi from Language drop-down list and click Save Changes.