Step 1 :
Given coordinates of the vertex is (0,0) and the coordinates of focus is (-2, 0)
Since the vertex of the parabola is (0,0) and also the focus lies on the negative x - axis.
The axis of the parabola is x - axis.
Hence the equation of the parabola is $y^2=-4ax$
Substituting for $a$ we get,
$ \Rightarrow y^2=-8x$ is the required equation of the parabola.