Change my password
To change your password, be sure you are connected to the project manager.
Then click on your name on the top-right of the screen. A dropdown list will appear; click on Change my password.

A modal screen will pop up, asking for your current password, please fill it in the first field.
Then enter your new password on the second field, and confirm it on the third field.

Forget my password
If you forget your password, after typing your email during the login process, click on Forgot password? link.

You will then need to confirm your email address, where a link will be sent to define a new password.
Enter a new password, matching the security rules, then try to login again.