Step 1: Copy this link: https://github.com/Steveice10/FBI/releases/download/2.3.1/FBI.ciaCould someone please re-upload the FBI QR code picture? (the current url gives no image)
Step2: go to this website (http://fr.qr-code-generator.com/), generate a QR code thanks to the url above, scan it with your 3ds (with FBI).
Step3: Profit!