There are a few different ways to add existing users to new teams:
1. You can go to the manage members page, search for the user at the top, click on the ellipsis icon, then click on "change teams". See below.
OR
2. You can go to the manage teams page, search for the team name at the top, click on the ellipsis icon next to the team then click on "add people". You can then search for the user and add them to the team. See below.
