How do you download music from our computer to the
It is hard to provide any useful suggestions without knowing the type of cell phone your son is using.
Normally he would put the memory card in the cell phone microSD slot (provided it can support 2gb card), plug the USB cable from computer to cell phone (if it supports this). Normally the phone will have also got some software apps CD which should be loaded to computer. This will provide the necessary functions to load music files to the phone.
Alternative to USB is bluetooth connection which both the computer and the cell phone will have to support. He can transfer music files that way.
I am not sure if he can copy the files directly from the computer to the memory card and play it on the cell phone as data formats are not standard. Also iTunes files need to converted to mp3 format. If these are protected iTunes files then it becomes a bit harder - best to burn a CD and then rip into mp3 format.
Once again these suggestions are useless if cell phone cannot play music (mp3 or WMA etc) files, does not have microSD slot, does not have USB or bluetooth support.