You can access via https://121webhosting.com/cpanel and enter your allotted username and password . You can find default set password and username in your order confirmation email received while ordering.
You can also follow below :
You can also access from client area
Login to https://121webhosting.com/client/
Go to Services from Top Navigation bar and click my services.
You can see your CPanel domain name and at right side there is a button "Active" click on it
In left side vertical navigation menu you will find option "Login to CPanel"
Click on it and you will be directly Logged In
