How to manually transfer music from PC to iPhone SE?

I'm trying to transfer music from a pc running windows 10 to an iPhone SE (newest model). Computer has apple music and devices apps and all music I'm trying to transfer has been downloaded onto the computer from CDs. I previously did this using iTunes but since I added apple music app to computer that is no longer possible. Devices app gives an option to manually transfer music, movies and TV but it doesn't seem to permit me to do so when I try and syncing seems to be the only option. I don't know what might be deleted/replaced should I sync and that's why I'm hesitant to do so. I'm not subscribed to apple music. I'd appreciate some suggestions. Thanks.

[Re-Titled by Moderator]