fourth-order Runge-Kutta method producing values for $f(x)=\int_0^x e^{-t^2}$ (confusing answer key)

Question

Describe how the fourth-order Runge-Kutta method can beused to produce a table of values for the function

$$f(x)=\int_0^x e^{-t^2}\ \mathsf dx$$

at $100$ equally spaced points in the unit interval.

The answer is a little confusing and not full so would someone please explain the answer? Answer: Find an appropriate initial-value problem whose solution is f. Solve df =e^{−x^2}, f(0)=0.