Can someone explain how KingSumo works?

I’m interested in doing a KingSumo giveaway to grow my email list… but I don’t really know how it works. Is anyone able to point me towards resources or walk me through it?

I’d be open to joining with other authors in a giveaway that I run if someone’s willing to help me figure out the process! I write clean fantasy for a Christian audience—I’ve published MG and YA, but my next novel is adult.