Lucky,
Thank you so much for taking your valuable time to reply. Boy, do I appreciate that.
I discovered that what I wanted was a Mask. I had not known of them. I wanted to paint out a background. A mask lets me "paint" invisibility (full transparency) easily. So, my issue is 100% resolved.
Thanks again. Every time I touch Artstudio I am in awe all over again that someone makes an incredibly wonderful program like Artstudio Plus.