The equation of a circle centered at $(a, b)$ with radius $r$ is given by:
$$(x - a)^2 + (y - b)^2 = r^2$$
In this case, we have:
* Center: $(-2, 0)$
* Radius: $3$
So, the equation of the circle is:
$$((x + 2)^2 + y^2) = 9$$
This can be simplified further as:
$$(x + 2)^2 = 9 - y^2$$
Or,
$$(x + 2)^2 = 6$$
Therefore, the equation of the circle with center at $(-2, 0)$ and radius of $3$ is:
$$(x + 2)^2 = 6$$