Where do you put the firend codes because I can't find out I barely got..

On your home menu of the 3DS and/or XL you'll see an orange face icon on the top of your bottom screen. Tap on it and it'll view your Mii registered for the system (if you have suspended software while doing this process your Mii will be playing the game aswell) and it'll show whether you're online or not. Now, once you tap your Mii, also known as your "Friend Card" information shall appear on the top screen. Under your Mii's name will be your Friend Code, give it to someone you're willing to trade Friend Codes with. Then tap another face in the top right corner of your bottom screen, choose to add the other friends' code via internet or via local. Local is done right next to each other, over the internet you will have to enter in the other friends' Freind Code. Doing so over the internet will take longer because you will have to wait until you friend does the same to his or her system. Once you both have each other's Freind Code you will be notified with an orange notification light. The orange light will also appear again once other friends and you are online at the same times. That is basically all there is to it, but it's WAY easier than it sounds. I may have over did the explaination for you, but atleast you've the answer you needed. Good day sir, or ma'am. ^_^