There have been several reports from people adding apps from the website and them not showing on the Home Screen, but yours may be the first of adding from the "Streaming Store", so this may not work. You can bring up a list of your installed apps by pressing Home 5 times, Up arrow twice, followed by Left, Right, Left, Right, Left. If you do it properly you'll see a list of your installed apps. Find Prime in the list and press Select/OK and there should be an option to delete it. Add it from the "Streaming Store" again. You can also delete an app using the mobile app by searching for it and if it's installed you should get the option to remove it.
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