Determine what variable in the equation functions as the moderator. For instance, take the example of a farmer's hours worked, the number of apples produced and the influence of weather on their growth. Weather moderates the farmer's hours worked and the number of apples produced. So weather is the moderator and has a causal effect on the farmer's work (X) that determines the apple production (Y).
Solve the point of intersection by taking the slope of the graph and multiplying it by X. In the above example, you would graph X and Y and then determine the degree of the slope.
Multiply the slope by the total apple production (Y) at the point where the farmer's work (X) equals zero. This provides you with the point of intersection using a moderator variable.