I thought you're referring to Shadow4 skin (hence the ss)
Add that line to the rainlendar2.ini file in the user folder, right after the "[DefaultSettings]".
About Yahoo Mail, I found something:
In the Calendar window, click on Actions, then Share...
In the popup select iCalendar
Here's a picture but on a Spanish version, so I hope the site is worldwide and the order be the same:
The only trouble is that is read-only. I mean, looks like there's no way to send an event to the calendar (unless I missing something).