This How-To is pretty comprehensive and should help.
[HowTo] Configure Plex to use embedded metadata (music)
If you have embedded tags in your music files using an app like MP3Tag or EasyTag, you should not bother trying to edit the tags within Plex. Changes you make in Plex are not written back to the embedded tags in your files. They are only stored in Plex’s database. You could end up with conflicting tags, and I don’t know how Plex reacts to that.
As to the difference between “Album Artist” and “Artist”:
Artist is basically the artist for the track. Album Artist is the artist for the overall album. If every track is by the same artist, then obviously Artist and Album Artist would be the same. If the tracks are not all by the same artist, then, generally, the Album Artist should be “Various Artists,” and “Artist” would be the artist for the individual track.
