How can I reduce fat from the lower part of my neck

If a person were serious, a constant and healthy way would be to roll your head to the furthest degree in a continuous slow and controlled complete circle, both clock wise and counter clock wise with lots of repetition this will tone your muscles.
I would start in two minute intervals two to three times a day and increase repation as your stamina builds you may start in a sitting position.
Also in the same regiment hold out your arms and rotate them in concise circles, make little circles and then in a separate exercise make big circles. Do this in both forward and in a reverse motion. The object is to maintain a controlled movement.