You can easily join a team after you are registered. You can also easily change teams anytime :)
Then you will be logged in (in this case you can see the user icon has changed)
Then click on the user icon again and select PROFILE:
(NOTE: this is an often-missed but important step)
Then find your event and click on "manage registration"
Then you will see an updated menu bar that includes the "TEAM" option - CLICK "TEAM"
Then click the "JOIN EXISTING TEAM" option:
(note: if you are currently on a team it will be displayed to the bottom left under "current team)
Then click on the drop-down arrow to select your desired team:
(NOTE: these are listed alphabetically but extra characters like "" and # can skew the display order for those team names)
Then click UPDATE:
That's it! You should now see your new/current team listed in the bottom left corner.