Just a note:
The site mentioned is only available to those living in the U.S.
The campaign form makes it appear as if you can write in from any country but you end up getting this message...

We're sorry but it appears that you are not eligible to participate in this campaign. This campaign is designated for constituents of the targeted decisionmaker(s) and based upon your address, it appears that you do not live in an area represented by the targeted decisionmaker(s).