How do you transfer MP3 songs from the PC to the cell?

I have downloaded some Mp3 songs from the net to my pc and want to transfer it to my cell. How can I do it ? Also plz tell if there will be any virus problem in doing so, also can I transfer .wma songs to my cell? Have to buy any USB cable to do so? My pc has a 5in1 card reader. It also has USB port. Plz help.