Forum Discussion
I'm a bit confused. Your title talks about accessing FYC Prime Video, but in your text you want to install regular Prime Video.
I never heard of FYC Prime Video so I did a web search and found this: https://www.amazon.com/Deluxe-Entertainement-Consider-Amazon/dp/B08D6W7V12
This sounds like this is an app Amazon has released for Android devices running the Amazon Appstore app. There is no mention of availability on Roku.
As for regular prime Video, there is a Roku channel app for this you can install from the Streaming channels option on your Roku TV home page. This requires a paid subscription. This can be obtained as part of an Amazon Prime subscription, or I think I've read you can subscribe to Prime Video only. When the app is installed and loaded click on the "gear" icon in the upper right and Sign In into your Prime account.