Click on Team, team window will be popped up.

Create a team:
Click on Create to create a team, you will become a captain. The Create button won't appear on team window if you are already in a team.

Join a team:
Click on Join and then click on the target captain. After he/she clicks on OK to agree, you will join his/her team provided that his/her member list is not full. If you are already in a team, the Join button won't appear on team window. Your request won't be sent out if the target player is not a captain.

Leave a team:
Click on Leave to leave your team. The Leave button won't appear on team window if you are a captain and not in a team.

Dismiss a team:
Click on Dismiss to dismiss your team provided that you are a captain.

Invite a member:
Click on Invite and left click on the target player to send out your request. If your member list is not full, the target player will join your team after he/she agrees. If you are not a captain, the Invite button won't appear on team window. Your request won't be sent out if the target player is already in a team.

Expel a member:
Click on the head portrait of the target member, and then click on Expel to expel him/her. If you are not a captain, the Expel button won't appear on team window.