You can only access and change passwords for users that are not private. To change a password or set a recovery email, navigate to Settings -> Addresses/Users and find the user you would like to access. Click on the “More” button (next to the “Add Address” button) and select “Login” from the drop-down menu.
You will need to enter your login password for the admin account you are currently using. Once you are logged in to the user’s account, the password can be changed in Settings -> Account -> “Change Password”.
When changing your password, you will be asked again for your admin account password. Then enter the user’s new password and click on the “Save” button.
From the user’s Settings panel you can also set a new reset/notification email. Again, you will be asked to enter your admin password to make this change.