This isn't as difficult as it sounds. First, we need to find the slope so we do
(y(2)-y(1))/(x(2)-x(1)) and plug in using the points we have:
(-3-3)/(2-0) = -6/2 = -3
Now we use the point slope formula which is y – y1 = m(x – x1)
From this, we again plug in using one point and the slope we have. Let's choose (0,3) because it's simpler.
We get: y-3 = -3 (x-0)
y - 3 = -3x
y = -3x + 3
I hope this helps. :)