You are new at this you say, so you need to spend more time exploring the Alexa app, and also learn where Help is located at amazon.com. It is a tab near top of page labeled Help. Click there and look in Device Support, find your device and look in that link.
Meanwhile, maybe this info can help with the app:
In app, go into Music,Videos etc, Find your Alexa device, such as the Dot you are using and select it. Go into Amazon My Music, Notice Playlists label. If you have made any they should be listed there, so select one to play.