Question about putting music onto ipod from itunes?

Okk well i have just got the newest ipod nano, the one with the video camera, and i plugged my ipod into itunes and successfully managed to put all my music from itunes onto my ipod (i cant really remember how i did it tbh so dont say you just do the same again :L) but since then i have downloaded more music onto my itunes, but i dont know how to put that onto my ipod? Ive plugged it in and everything and the itunes comes up and it says 'Lucy's ipod' so its recognized it (btw im not called Lucy im just giving an example :L) but what next? Thankyou.