To access the AutoSizeScale just edit the dashboard and select the widget on the right. Scroll down in properties and there it is.
The way I choose the right scalar is: Choose either the width or height of the dashboard (800x480) and divide the width or height of your screen by it. If you would have a let´s say 1024x768 screen the scalar would be 1024/800= 1,28. Check again though if the other parameter of height or width is not too high for the screen resolution.
