Here's the page for signups: https://listfortress.com/league
Here's the list of players already signed up (177 as I write this post): https://listfortress.com/season_seven_surveys
As you can see, List Fortress will be used to manage the league, but you can also treat http://xwvassal.info/ as a central hub to get to your specific group listing, to access the vassal guide, etc.