You should be able to connect your phone to your PC via a USB cable without any additional software (other than drivers).
Once you're connected, open Windows Explorer (Windows Key + E) or select it when prompted. You should see your phone listed under My Computer as an external drive.
Simply expand folders under the phone then drag and drop the music files from the PC folders to phone folders.
When you plug the USB into the PC, your phone may prompt you to select a USB mode. Depending on which version of Android you run select the option that is called something like Media or the option called something like external drive.
