PicPick_draw / create solid circle_save w/ transparent square background

In PicPick is is possible to draw a circle & save it where nothing of the default square / rectangular background shows. Either background (of original rectangle) isn't saved or is transparent. Say, to create a round icon w/ no square background.

In PicPick, creating the filled circle's no problem or getting it the right size. But can't figure out if it's possible to save as a circle w/ no square background. I don't see an option for a transparent background.

Maybe just need to use another app. Icons or other images often have square backgrounds of a different color from image. But many are circles or other free form shapes w/ no background (perhaps transparent). To not have a square background, will I have to use some other app?
Thanks.