Laptop :
1) Install the driver DJM Nexus from Pioneer before your session on your laptop
2) connect the USB cable from the DJM to your laptop
3) open your DAW (Audacity, Reaper, Ableton…) - arm a recording track
4) go to preference system Audio and select the DJM pilot

Mobile :
On your phone, you can use DJM Rec if you're on IOS and on the DJM-900NX2. Don't forget to bring your Lightning to USB A cable.