Welcome to AC!!
Did you plug your phone in VIA USB? If it recognizes it that way, you can just browse the mounted drive (your phone or SD card) and drag and drop the files. Your phone's media player(s) should automatically locate the music.
If your computer is not recognizing the phone when you plug it into your computer, when the USB icon shows up in your notification area, select it and make sure you have the Mass Storage option selected.