Step 1 corresponds to setting the distance from focus to the point equal to the distance from directrix to the point. Notice the coordinates of the focus and the directrix being used.
Step 2 corresponds to finding the distance from the point on the parabola to the focus. Notice de formula for distance being used with the coordinates of the focus.
Step 3 corresponds to choosing a point. Hence " Use (x,y) "
Step 4 is writing down the equation of the parabola. Notice a complete expression describing it.
Step 5 is finding the distance from the point to the directrix. Notice that the formula for distance is being used again; with the coordinates of the directix.
Step 6 is squaring both sides and simplifying.