So I finally earned Co-Leader with my clan, super stoked to be a Co and help people out.

Anyway, I dont want to make a mistake when starting a war. After hitting the Start War! button, what happens next? I was going to hit it and see what happened but I dont want to make a mistake and inadvertently start a war that isn't optimal. I'm assuming that I'd choose the roster of war participants, then it would start the search, but I haven't done this before. Thanks in advance!