Sling's FAQ on this issue is out of date and should be updated.
I have a smart Samsung TV and just bought the FireTV stick.
After installing and registering the stick, SlingPlayer is NOT listed as an app.
You have to go to your Amazon account, search for SlingPlayer for Fire TV
and then download. Only then will it appear in Fire's app list.
My issue: the remote that appears on my laptop version of sling, does not appear on the Fire TV. I have to use a less user friendly version that appears on the screen.A