If you have a FB account and a Google Mail account you can switch between the two by logging off and then logging on with the other account. Go to the 'Gear' (Settings) button at the bottom of the left hand menu and scroll down. Log Off is the last option, it then goes back to the TE login screen and you can select FB or GM from there. You will need to have a Google Mail account for your other team, nowadays GM asks you to set up a Google Play Games account for interfacing with TE.
If you haven't got FB but want another GM-based team, create another GMail account, and then another Play Games account to go with it. The same procedure to switch between the two, but ignore the FB option. When you selct GM, it connects to Google Play Games and then there's an option to select the GMail account you want to use.