Rearranging The Registration Page?

I’m trying to rearrange the registration page on my site with s2Member. I have the design all figured out and everything looks good. But, I’m trying to place an additional field in the registration area that explains (is a checkbox) the username. How would I place that up under where the username goes instead of at the bottom of the form?

Thanks!

https://wordpress.org/plugins/s2member/