You can change your password in your user account settings. You can access these settings by clicking the person icon in the top right corner and then choosing Account settings.
Now you can view your account settings and the first item is Change password with three text fields. Enter your old and new passwords in these boxes. The last field is a confirmation of your new password, so you’ll need to enter it twice. Finally, click Change password and your password has now been changed.
You will not receive a confirmation of this, so make sure you store the new password in a safe place.