We wish we had one easy answer for this! There are millions of playlists on Spotify, with even more millions of listeners. To get on a Spotify playlist you will need to get in contact with the curator of the playlist and send them your music, with a short pitch on why you think your track should be included in their playlist.
Take a look at the playlists you already follow, and do a search for others that would be appropriate for your sound. Find the curator's name and do a search for them online to see if you can find an email address or social media account for them. Don't be disheartened if you can't always find the playlist owner online, it's not an easy task!
When you contact the playlist curator, make sure you are friendly and professional, and include a note about yourself and your music, and why it would be a good fit for their playlist.