Very simple.
Let's say you have an equation.
f(x) = x^2
You are asked to find the value for y when x equals 1.
The new equation is: f(1) = (1)^2
f(1) = 1
When x = 1, y = 1.
The same concept is applied here.
In the graph, where does x equal 0?
It equals zero at the origin.
Is there any y-value associated with 0?
Yes, there is.
Y equals five when x equals 0.
So
h(0) = 5