How do you put friend codes in your ds

go down stairs at Pokemon center and recice pal pad go register name and code
It depends what game you are playing though, if you play animal crossing you go to the gate house and get your freind code by clicking on the guards and asking "friend code!" they will make sure you are connected (wifi) and then they will give you your code. Now, to answer your question, to put in friend codes on your friend roster, you can press the x button and click on the heart, then click register or something, you can add the freind code there.
If you figure it out add me as a friend!
Name: Erin
City: Merryvil
Friend code: 3653 - 0346 - 7059
( i usually play during the weekends, or Friday afternoons ) seattle time!
hope this helped! ( i also play Mario kart!)