Question: numark idj3 how to use?
Answer: Connections. Connect the iDJ3 with your computer using the provided USB cable. ... 
Drivers. Install the required drivers from http://www.numark.com/product/idj3. ... 
VirtualDJ. Install VirtualDJ 8 from http://www.virtualdj.com/download/index.html (in case you have not done already)