Can anyone show me how to use the Signup Module? I don't see anything in Structure or Add Content. I'm sure I just missed the link somewhere but I just can't figure out where.
I had the same problem, I only recently figured out that you have to go into the content type that you want to enable it for, and specifically enable it under the Signup tab. In terms of using it, you mentioned add content. Well, the sign up module is not meant to be added. It will automatically display a form to sign up as long as you enable it for the content type.
admin/config/people/signup is where the settings page is located.
admin/content/signup displays "all signup-enabled posts, and open or close signups on them"