Shift+Click or Click/Tap+: Add a Character to the Moon list.
On the top area:
Click/Tap: Remove an element.
Drag: Move an element.
Ctrl+Drag: Duplicate an element.
Shift+Click or Click/Tap+: Toggle the element Spark status.
Others:
Change the number of rolls next to the Filter.
to generate an Image of your spark. You can then right click/hold touch it, to Copy or Save as (It might not work on some phones/browsers, please take a screenshot instead).