Once you're logged in, go to your control center and click 'teams'.

To quit your current team, click 'Part Team'.

To change teams, quit your current team. You can then return to the Team section of your control center where you can choose between 'Create a team' and 'Join a team'. When you choose to create your own team, you will have to fill out a Team name, Team description and a optional password (passwords make your team invite-only). If you simply want to join another persons team, click on the 'Join a Team' link and a search will appear. You can search for teams with either the teams' ID, name or description. After you've found the team you wish to join, simply click the 'Join' button.