Login to your WHM or go to cPanel >> Click on Web Host Manager(WHM)
Go to Account Functions >> Click on Create a New Account
if you're new then first you need to create a Hosting Package(Open in New Window)
In a Domain Information: 
Domain:  Example.com
Username:  example1  (Max 8 chars)
Password:   For Strong Password, use "Generate a Password"
Email:  Please enter your own email - For Your Security: do not use your client email
Package available:  Select Your Package
Settings:
Locate:  Select cPanel Language(Default Language is English)
DNS Settings: (Very Important)
If your client want a Custom Name Server then mark on box or if you want to use our name server or your name server then do not mark on box.
Mail Routing Settings:
Select this option:  Automatically Detect Configuration (recommended) more »
Last Step:  Click on Create  - (In Account Creation Progress, do not close or stop window)
