However if you wish to download the music directly from YouTube then all you need to do is open up YouTube and search for the song that you want to download. Make sure that you find a version of the song that is clear or high quality, preferably not the music video as a lot of music videos contain scenes or noises that aren't on the official song. Preferably you should choose one that someone else has made which shows the lyrics.
Then what you need to do is to open a separate window and perform a Google search for 'YouTube to mp3'. Open up this page and then go back to YouTube. Copy the address bar that is at the top of the page and then paste it into the YouTube convertor and press convert. Once it has converted download the file directly onto your computer.
Once the download is complete, insert your USB into your computer and then open up the folder. Look in your download page to locate the files that you have just downloaded and then drag and drop them into your USB folder. However if you wish to keep a copy of the music file on your computer then you should just copy and paste them into the USB file.
If you are transferring the files to another computer then all you need to do is insert your USB stick into the computer, open the folder and then copy and paste them across into a file on the computer.