In the upload form you can provide your Spotify Artist URI related to the artist profile that you want your release to be assigned to.
If you've missed that field and your release went online on a new artist profile with a different Spotify Artist URI, please send an email to support@magroove.com and we'll fix that for you. The email you send us must contain the Release Name of the release you want to go to your previously existing artist profile and the Spotify Artist URI related to it.