To buy music on iTunes for your iPod or other Apple device you need to be able to connect to the internet through your Wi-Fi or cellular network, or you can purchase music from your computer that has internet access and transfer what you buy over to your iPod that way. You can download the latest version of iTunes to your computer by going to Apple iTunes Download.
When you download iTunes to your computer you will need to set up an iTunes account. Using the email address you have associated with your iPod makes that easy. Then, all you have to do is log onto iTunes and browse or search for the music you want to buy. When you click on “Buy” the music will begin to download. The price for the music is charged to your Apple ID, so whatever payment option you have set up for that will incur the charge.
If you use your computer to buy music from iTunes you can transfer it to your iPod or other Apple Device by connecting the device to your computer. When iTunes recognizes your device you can choose to automatically sync all songs or a particular playlist to your device. You can also choose to manage music manually and this choice will make sure that music currently on your iPod doesn’t get erased from the syncing process.