Just ask Alexa to…
“Launch NonStopPlay Radio“
or “Launch Pure Dance Radio”
If that doesn’t work immediatey, you may need to enable the skill before you can listen. To do this you can ask “Alexa, enable skill” then ask for “NonStopPlay Radio” or “Pure Dance Radio”
Once the skill is enabled you can just say “Alexa, Play NonStopPlay Radio” or “Alexa, Play Pure Dance Radio” to listen!