A new tab for the World Restructuring feature is now available in the in-game World vs. World panel. On this tab, you'll be able to choose which of your guilds you'll want to play with during the World Restructuring beta event. Please choose your WvW guild before 11:59 p.m. Pacific Time (UTC-7) on September 23, or you may be matchmade on to a team as an individual player. The first weeklong beta event for the WvW World Restructuring feature takes place from September 24 to October 1.
https://en-forum.guildwars2.com/topic/101849-game-update-notes-september-21-2021/?tab=comments#comment-1467993