anyone know how to use sd card for my binatone x350?

can anyone help please.i have purchased a sd card for my sat-nav ime assuming that when i connect to the sat-nav i can then use the usb cable and plug it into my pc.i want to go into pictures and download pics from my pc to the sat-nav.i pressume that is how it works.when i connect to pc nothing happens.?.i must be doing it wrong can anyone help please.