The effective area parameter is used in our simulation to model nonlinear effects (not dispersion), so you should use the effective area that is attributed to the fiber that you are simulating. A common value and the default we use is 80 um^2.
In a real life scenario a DCF might have a different value since the waveguide might have a different structure (smaller or bigger). You can use OptiFiber to calculate its effective area or you can use the link below to read about a similar topic. I made a matlab/Optisystem file that demonstrates how to calculate the effective area from a spatial distribution.
Regards