Answer
See the picture below.
Work Step by Step
By calculating the values of $f(x)=\sqrt{x}-2$ (with blue) and $g(x)=\sqrt{x}$ (with red) we can see that the value of $f(x)$ is 2 less, than $g(x)$ for each corresponding x.
In order to graph the exact parent graph, here is the table of values:
$g(0)=\sqrt0=0$
$g(1)=\sqrt1=1$
$g(2)=\sqrt2=\sqrt2$
$g(3)=\sqrt3=\sqrt3$
$g(4)=\sqrt4=2$
(The square root function is not defined for negative numbers.)
Therefore the graph of $f(x)$ is exactly the same as the graph of $g(x)=\sqrt{x}$ but is translated 2 units down.