Dear Bro hayder9970,
You only need to press the button to on certain gears.
For example, N to R, R to P, P to R and D to S(FD2)
Changing from the following does not require you to press the button. R to N, N to D, D to N and S to D (FD2)
I think all these should be stated in the User Manual of the car. I think I remember seeing it somewhere before. I think you should check it out if you still have doubts.
