This widget is being phased out. Instead, use the Needs widget.
Add as many images as you wish, keeping in mind they display in rows of 3-2-3-2-3, etc. with the rows of 2 images showing larger images.
You can write some text that displays under the collage. Collages show the items in rows of 3-2-3 - you can probably go on forever! Tick the Featered Item box for the image to display on mobile.