newbie question - how can i put mp3s on storage card?

[knives of ice]

i can't seem to figure this out. i don't have a card reader on my computer so how can i transfer mp3's from my computer and save them directly on my micro sd card? i can figure out how to send over bluetooth to the phone but the mp3s are too big sometimes and take too long to send. is there a simple way to just save directly to the card? thanks.