I cant find the Arduino and actually make Scada talk to it...
I downloaded the sketch that was linked to in step one.
I downloaded the software that was linked to in step two. I installed it. I ran the movie, stopping if often. I recreated the project described, except that I had to use different pictures for the LED on and LED off images.
I uploaded the sketch to the Mega, and tried running the Scada application. It didn't seem to work. I switched to a Duemilanove, and still nothing but a blank form in the Scada application. I discovered that I had three forms, two of which were blank. When I deleted the two blank forms, the Scada application appeared correctly. I had several icons in the task bar some of which were green and some were red. I closed the Scada application, and killed all the processes related to it.
I started the Scada application back up, and ran it. My form with buttons appeared, and three icons in the task bar lit up, green. I was able to make the light come on and go off on the Duemilanove.
I closed the application, stopped Scada, and unplugged the Duemilanove. I plugged in the Mega again, and got the COM port number it was using. I changed the Scada application to use that number. I ran the Scada application, and got all the icons. Pressing the On button turned on the LED on the Mega. Pressing the Off button turned it off.
So, I think you need to describe what you did.
The movie, in my opinion, was by no means the best way to define how to use the application. Screen shots and explanatory text in html pages would have been far better.
And, I want to add more functions, but I cant find any info or logic "system" to tell the Arduino what I want....
You'll need to define this a little better. Clearly, the link between the Scada application and the specific pin activated on the Arduino leaves a bit to be desired. But, more actions can be defined in the Scada application, using more than register 0, and the Arduino sketch can be extended to handle more than register 0 actions.