How do I get my music on iTunes/Amazon/Spotify/Google/etc?
There are a number of ways. If you’re being distributed by a label or a distributor like IODA, TheOrchard, or some others, this stuff is often handled for you. If you’re an indie, you can use a service like TuneCore.com, CDBaby, DistroKid, or Reverbnation (among others) to package your content and put it on a variety of digital services around the world.
If you wanna get even more indie, there’s bandcamp.com, which doesn’t license to other services but also has a different pricing model and is very artist-driven.