Find an equation that says thatP = (x, y) is equidistant from F = (2, 0) and the y-axis.
Since you title this "parabola", I suspect you already know the answer. However, the derivation is this:
The distance from (x, y) to (2, 0) is $\displaystyle \sqrt{(x- 2)^2+ y^2}$ and the distance from the (x, y) to the y-axis is simply x. To be equidistant, we must have $\displaystyle \sqrt{(x-2)^2+ y^2}= x$
Square both sides and simplify.