Here are the ways to enable ALT.
If you are in front of your Amazon Echo or Echo Dot, say “Alexa, enable alt one oh two three”.
You can also search for “ALT 102.3” on the skills section of your Alexa App.
Going through the Amazon site is also another way to enable ALT 102.3 by clicking HERE.
Once enabled, you can say “Alexa, play ALT one oh two three”.