scattering nanoparticle cross section

Hello
Sorry my English is not perfect.

I have to make a simulation of a gold nanoparticle (R = 20nm) hit by a plane wave.
I have to get a chart:
x-axis - wavelength (200nm-800nm​​) or frequency
y-axis - cross section of extinction

I use COMSOL 4.3
I saw that there are other threads about it. are appointed the following tutorial:
scattering Nanosphere
radar cros section
rcs sphere

I still do not know anything about COMSOL.
there is a tutorial fit my problem?
how can I proceed?

thanks for your help