The Record Label promotes the release in various ways. Depending on the genre it will be any (or all) of the following:
Social Media
Think of messages on Facebook, Twitter, Instagram mentioning the release and linking to them in sale & stream stores. In addition, the Record Labels engages with everybody who tag the Record Label about the release, thus increasing exposure.
Content channels
Upload the release to content channels such as Soundcloud and Youtube with a detailed description linking to all of Artists social media.
Music Promoters
Increasing exposure by pitching the release to music promoters. This can be anything and anybody from a music promotion channel to national radio hosts and massive playlist curators on stream portals such as Spotify. Do note that results vary per release since factors as genre, popularity, availability, technical issues and good old judgement when somebody has a bad day.