Create an Apple Digital Masters (aka Mastered for iTunes) Product

Choose the Hi-Res Audio product type when creating a new product. All Apple Digital Masters audio assets must be 44.1KHz/24 bit or 96KHz/24 bit quality or will be rejected on upload. The same quality must be uploaded for every track on a given release.

Apple also requires that Apple Digital Masters products follow specific mastering guidelines, including being mastered by Apple-approved mastering studios.  Therefore you are required to enter the Mastering House Email field on each track, or it will not deliver to Apple Music / iTunes.

For more information, see Apple's own Apple Digital Masters page.