The center of the circle is at: $ C = \left(5, 6\right) $.
The radius of the circle is $ r = 6 $.
A circle with center at $ ( \color{red}{h}, \color{blue}{k}) $ and a radius of $ r $ has equation $ (x - \color{red}{h})^2 + (y - \color{blue}{k})^2 = r^2 $.
In this example our circle equation can be written as:
$$ \left(x - \color{red}{ 5 } \right)^2 + \left( y - \color{blue}{ 6 } \right)^2 = \left( 6 \right)^2 $$So, we have: $ \color{red}{h = 5 }$ , $ \color{blue}{ k = 6 }$ and $ r = 6 $.