how to download mp3 music onto iPhone

I wish to transfer an MP3 music file from my laptop to my phone. I managed to load the file to my Apple music library but iCloud music won't allow me to add this file to my iCloud music library: "This item is not eligible for the iCloud Music Library"

I want to access it on my phone directly and not via iCloud. The Summary/Options do not offer the option to manually manage MUSIC, only VIDEOS.

"MacBook Pro macOS Sierra version 10.12.6, 2.4 GHz Intel Core i7, Memory 8GB 1333 MHz DDR3"

"iPhone 6 version 10.3.3 (14G60), available 8.88GB"