You can add a featured artist to a track either when uploading or afterward by submitting an edit through your release page.
Importantly, this does not use up extra artist slots on your eMastered plan.
Be aware: if the same featured artist appears on every track of a multi-track release, streaming platforms require them to be credited as a Primary Artist instead.
Adding a Featured Artist During Upload
While uploading, look under the "Track" section for the option “Yes, Add another artist to track title:
After enabling it, type in the featured artist’s name and the role they played in the track.
If desired you can also check the box to add this artist to all tracks on the release.
Adding a Featured Artist After Upload
For already released tracks, open your Catalog page, select "Edit release," then click “Add another featured artist.” From the dropdown, choose "Featuring," and enter the artist’s details.
Submit the edit request once complete. Most services process these changes within a few days, but it may take 1–2 weeks for all platforms to update the metadata fully.