I have numerically solved a differential equation and obtained numerical values of $\frac{dy}{dx}$ at different points of the domain space. How can I now obtain numerical values of $y$ from these values of $\frac{dy}{dx}$?

It is not possible to obtain $y$ directly from the differential equation. Finding $\frac{dy}{dx}$ itself required computation of an elliptic integral.

I don't want a computer algorithm; I want to write it myself. Just tell me the process to do it.