As you enter Artists on a product or track, Central will look up each Artist at Apple and Spotify and return matches based on the text entered. To view these matches, simply click the box with the Apple / Spotify logos next to each Artist's Role.
If no matches are returned - for instance, if this is the artist's first release - then you can choose to send the artist without an ID and the music service will place them on the most appropriate artist.
If one or more matches are returned - for instance, if there are multiple artists in the real world with the same name, or there have been multiple artist pages created in the past for the same artist - you can click the blue icon link next to each one to view the artist page at Apple or Spotify and determine which one is correct.
Although currently optional, it is highly recommended that you take the time to choose the correct artist page for every artist you enter. For older content or recent new Submissions for which you have not made the choice, you can manage it in Change Requests as well.
If you need to move an artist from an incorrect artist page at Apple or Spotify to its correct page, simply create a Change Request as usual and use the Artist ID feature exactly as you would in Submissions.
The artist will already be present on the product and Central will automatically look up any matches at Apple and Spotify. Make your selection, submit your Change Request, and the change will be delivered to Apple as an ordinary metadata update. The end result will be the product or track in question being moved to the appropriate artist page at Apple or Spotify.