Once you have logged into the account, you simply need to select the settings tab, followed by users. You will then be taken to the main user page where you can change the password for the user.
All you need to do is select the user you would like to amend and change the password the user has.
Please ensure that the password meets the requirements highlighted in the text box below the password strength indicator.
If your password does not meet the requirements you will not be able to change the password.
Once you are happy with the changes to the user simply click update to be taken back to the users screen.