Spotify’s Discovery Mode is a promotional tool currently in beta and not yet widely available.
To participate, artists must meet the eligibility requirements for both their artist profile and individual tracks as described here.
If you qualify and are interested in using Discovery Mode through Spotify for Artists, fill out this application form: https://spotifyforartists.typeform.com/to/OcfFq0oE.
Make sure to input your Spotify Artist URI correctly in the form—Spotify won’t be able to process your request without it. Keep in mind that submitting the form doesn’t guarantee access.
If Spotify grants access, they’ll contact you with details. You’ll receive an email from them with instructions on how to launch a Discovery Mode campaign via Spotify for Artists.