How do you get the add button to apeare to be pressed on the3ds?

To get the "Add" button to appear on a Nintendo 3DS, you typically need to access the specific application or feature where you want to add content, such as the Friends List or the Nintendo eShop. Ensure that your 3DS is connected to the internet and that you are logged into your Nintendo Network ID if required. If you're in the Friends List, the "Add Friend" option should appear when you're on the appropriate screen. If you still don't see it, try restarting the system or checking for any system updates.