You must first leave your current team in order to create a new one.

The actions listed here to make yo leave your team simply:

Visit the Team tab.

Click "My Team"

You will see the "Leave" option.

Afterwards, complete the following procedures to establish your own team:

Visit the Team tab.

Choose "Create" by tapping it.

Set up your team's information (name-logo-description etc.)

Just hit the Create button at the bottom of the page to finish. The cost of building a team is 100 coins!