Not sure what phone you have but either check the Apple store or Google play for the Prime Video app. Another way is to open the browser on your phone and open your Amazon account and watch from there. If that doesn't work you can always hotspot a device from your phone and watch it on the device. Bad thing with the hotspot is your limited to 5Mbps and probably could only watch it in 480p, maybe 720p. Some video streaming/apps Visible also limits some of them on your phone to 2.5Mbps which is 480p streaming at best.
