You can add manually customer details by following the below-given steps:
1)Log in to the Admin area in WHMCS.
2)In the navigation menu, Under Clients, click Add New Client.
3)On the Add New Client menu, Fill out the client’s details.
4) The minimum required fields are First & Last Name, Email Address & Password
If you want an email notification sent to the customer, click the checkbox next to Tick this box to send a New Account Information Message.
5)Click the Add Client button to save what you entered. You will then see a summary of the profile you created.
