The process is a bit confusing indeed.

https://isocpp.org/std/standing-documents/sd-7-mailing-procedures-and-how-to-write-papers
explains that you need to get a paper number first and email Nevin to
get a number (email is linked on that page). Once you have a paper
number and your paper is in shape (i.e. the document header includes
that paper number and all that), you email that back to Nevin.