One word that matters in this discussion, is Geo Blocking. You will find that included perks of Amazon Prime are not available to you outside of the US geography, so you have you use a little bit of ingenuity to circumvent this. So, to work around the geoblock of Amazon TV, I recommend Unlocator.com
Sign up for a free trial after you receive your FireTV, through the above link, and enjoy!
You can do this both simply, and a tad more advanced. If you only have the 1 FireTV, use the simple method with just unlocator. If you have also Chromecast and AppleTV, you should use the more advanced version with a dedicated router.