i bought a ipod shuffle but itunes can not showing up

Make sure you look on the iTunes window, in the sidebar along left side, under DEVICES.

If you are connecting it to a USB hub, try a port that is directly on your computer.

If that does not help, try shutting down (powering off) your computer. Reset the iPod shuffle using this procedure

http://support.apple.com/kb/HT1655

Then, start up your computer, with shuffle NOT connected. Run iTunes. Connect shuffle.