As Administrator, you can change password for every user in your team. To do this, go to account drop-down menu, [Team name] settings, and choose the tab "Users":
Click on the user name you need, and you'll see user details panel on the right. Use button "Change password". In the pop-up window please enter the new password, repeat it and click "Change password".
When you press "Save changes", the password is successfully changed and the user gets a confirmation email.