Hey there, the easiest way for most people is to just plug in your USB cable, go to notifications or slide bar down, select USB Connected and mount as storage device. If your computer is has internet access, it should automatically download the drivers for the phone if any are needed. You should then see your phone's SD card listed as a mounted drive in My Computer or in Finder for mac. Create a folder here and call it Music. Now it's just drag and drop from here. When you're done, you can normally just unplug the USB cable. When the media scanner is done and the SD card is accessible again, open the music player of your choice, and there should be all the new music you uploaded. Hope this helps, we all gotta start learning Android ABC's somewhere
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