USB cable for T-mobile Tap phone doesn't work why?

i wanted to put music on my phone and i plugged it in and i was not recognized. i looked in my phone's booklet and all it said was if it didn't work just try again which i did so many times.the first time i tried it the same thing happened(this is my second time trying it). i searched it on Google but didn't get any good information. does any know what's going on.