Spotify provides artists with a straightforward method to submit music for playlist consideration.
To be considered, Upload via MusicDigi at least 21 days before the planned release date.
When you see the new and unreleased track in your app Spotify for Artists, select the track for playlist consideration and submit it to Spotify's team.
Check out Spotify's guidelines on pitching music here.
Here's an article that explains how Spotify's curators make decisions.
Best of luck!