Complete the squares for both x and y.

$\left(x^{2} + 8x + 16\right) + \left(y^{2} − 12y + 36\right) = 12 + 16 + 36$

$\left(x + 4\right)^{2} + \left(y − 6\right)^{2} = 64$

This is the equation of a circle whose center is at $\left(−4, 6\right)$ and whose radius is $8$.