How to Correctly Implement this Schematic Circuit including two MOSFET?
The cited article assumes that the control signal has the same full swing, from -VDD to +VDD. If VDD is 12V, the control signal of 5V in amplitude will not do the job. At some intermediate point both transistors will be open, and the entire 12V will be shorted by them, and transistors will be fried in no time.

To control a 12V motor in both directions, you should be using a H-bridge.