To create a team, locate the Add New Team button in the lower left corner of the dashboard, and click it.
Fill in the team name (required), and also any other options you'd like, such as a Slack channel to notify the team, a notification email, and a helpful description (such as the team's owner).
You will also have the option of changing the team color if desired. This can be done by clicking the Color palette near the bottom left of the screen.
When you've filled in all desired fields, click Create Team at the bottom left of the screen.
That's all there is to creating a new team. If you navigate back to the team dashboard you'll see the new team created.