How do I use a streaming service with my iPhone 7?

I am intending to get the streaming service from iTunes music. I have never used it before. Is there a good resource that will explain the process to me? I need to know how to set it up, how the streaming itself works, and what are the many possibilities to use it to hear abundant amount of music on my iPhone 7.

I would like to use Siri commands to simply make my request for a song or album, and to save and also get new song ideas from the service.

I would appreciate any help to start my venture of listening to music this way.

Thanks!