If you need to change your cPanel login credentials you can do so as follows.
If you need to allow access to a third-party vendor but do not want them to have access to your entire account, you can provide them with cPanel access. This is generally sufficient, and they can access it by typing their domain/cpanel.
Log in to your client area
Select the service you would like to change
Change the password. Make sure it is a strong one.