If you want to change your password, please log in to your account and and click "settings". On this page, in the menu to the left, click on the “Account & Privacy” heading and then click on the “Email & password” link. This will bring up a page where you can change your password. Enter your new password, confirm your new password and click Change Password. Your password is then changed immediately.
If you have forgotten your password and cannot log in, you can click the "Forgot password" option on the login page and follow the instructions to set up a new password.