You can access your cPanel by logging into the 'Client Area'. However, if you have forgotten your client area login details, please view the following help article - 'I've Forgotten My Client Area Login Details'.
To access your client area, go to the following - Client Area.
You will then be required to enter your login credentials for your account by completing the 'Email Address' and 'Password' sections followed by the 'Login' button. If you have forgotten your password, you can reset this via the 'Forgot Password?' option.
Select 'Services' from the top menu followed by 'My Services'.
From the left hand side menu, under 'Actions', choose 'Login to cPanel'
This option will have now logged you automatically into your cPanel section.