Each pass through loop, see if a switch is pressed. If it is, but was not before, record the time.
Each pass through loop, see if the button is pressed, and was pressed before. If it is, see if it has been more than two seconds since the button was pressed. If it has, do something.
You know, I presume, how to check that a switch is pressed, and how to use millis() to observe the "time".