It's easy to change the email address or the password of any user in your account. Just click on the top right navigation where your thumbnail image is and select "Workspace Users". Next, you're going to click the actions dropdown next to the person that you need to edit. Select "Edit". Along the very top, this is where you can change their password. You will need to enter it twice so you can confirm it. The individual can also change this on their own even if they aren't an admin by going to user preferences. If they need to change their email address, they can also do that within user preferences within their own account. And if you want to change it on their behalf, you can go in and change this using the email field. Once you're done making these changes, you're going to scroll to the bottom and click "Save".