Complex sentence: "Delilah" was released as the second promotional single on 19 May 2015, for digital download only; then was later given an official release as a single along with a music video on 21 October 2015.
Split into simpler sentences: Delilah was released as the second promotional single on 19 May 2015, for digital download only. Five months later, the song was given an official release as a single with an accompanying music video on 21 October 2015.