I have a new 3ds XL as well, what I did was take a screenshot, and then at the bottom right hand corner there should be an orange button and when you click on it, a box will pop up that says something like "open Nintendo 3ds image share?" Click yes or whatever that it says, and then it should take you to pick two options: upload your photo to Twitter (which is what I did) or Facebook.
They'll ask you to log in, and once you do that it'll take you to your Nintendo 3ds Camera where you can select the picture you chose, and it'll upload it to whichever account you chose
after I uploaded mine I just went on safari and saved mine cause I'm on an iPad rn