Does anyone want an easier way to do this; then here you go.
Open Twonky app on FireTV.
The only other device needed is a Windows PC (maybe a Mac can do this, too, but I doubt it.)
Select music from your source (via Win File Explorer) I can access my entire media collection from my PC, hope you can, too.
So, I select a complete album, mark/highlight all files in album. Now, right-click on those highlighted tracks and notice the "Play To" choice on the pop-up menu and select Twonky on Fire TV to play it to, press enter and enjoy that album on the TV, in album order and with album artwork on screen.
If you cannot do this, then likely your Windows Media Player is not configured correctly to share your media with other devices. OK, maybe its not easy for some who have not done this, but it is easy, so ask if you need help.