How do i enter the code into an 04 nissan micra

You know the buttons you press to get each radio station up?
(1,2,3,4)
if your code was 6789 you would press no.1 six times, no.2 seven times, no.3 eight times and no.3 9 times.
then when your code is in you press the the button that looks like this ^

it explains it all in the users manual, if you have it.

hope you understand