How do you log out of iTunes in order to use a different iPod/iPhone/iPad on it?

When I open iTunes i get this message…”Another user on this computer is uisng the iPod software, so iTunes is unable to communicate with this iPod/iPhone/iPad. please ask the other use to log out.

How do you log out?

The answer to this question is:
iTunes > Store > Logout or another user is logged in either your account or in another