Sign up Box in the middle of the post

Hi there,

Does it have to be placed in the same place for every post? Does it have to be in the middle of the post?

This is quite tricky to do as there's no hook within the content of posts/pages. You'll need a plugin for this if you want to dynamically place the form on the same place for all the posts.

Perhaps you can consider placing it after the post? You can use generate_after_content hook for this.