two questions about images

[Andrew]

Hi everyone.  I have a couple of questions about images.  When 
importing an image ("as control"), how do you make sure that it goes to 
the data-bank place (what is that called?) so it can be accessed from 
every card, rather than just being imported to one card.

Also, say I have one image and another image on top of it.  The top 
image is a non-square image, like a person.  However, when imported, 
there is white all around the person to fill out the square, and you 
can tell since it's sitting on top of the back image.  How do I tell 
Revolution that I want the white part to be transparent?

Thanks so much!