o connect a compatible Bluetooth accessory: Select Settings > Controllers and Bluetooth Devices > Other Bluetooth Devices from the Fire TV menu
To access Prime Music, you must have an Amazon.com account, a U.S. billing address, and a payment method issued by a U.S. bank. Prime Music is not included during the free trial period of Amazon Student memberships, or for invitied household memebers on a shared Prime account.
Some frequently asked questions about the student discount.
Source: Student discount FAQ – Spotify
You can also make Spotify the default player from your Amazon online account page:
Log in to your Amazon Alexa online account.
Under Music Services, select Choose default music service.
Under Default music library, choose Spotify.
Alexa will now automatically play music from Spotify, so there’s no need to specify this with your voice commands