cPanel will automatically generate a free hostname certificate during nightly maintenance as long as the hostname resolves to the Main IP address of the server. However, you’re welcome to use the following procedure to manually generate the certificate if you need it sooner.

If you need to replace a third-party certificate with a free hostname certificate, you can remove the third party certificate with the following steps:

1. Login to WHM as the root user.
2. Navigate to: “Home »Service Configuration »Manage Service SSL Certificates.“
3. Click on the “Reset” link to remove the existing certificate and replace it with a self signed certificate.

In order to install the free hostname certificate use the following steps:

1. Login to the server via SSH or Terminal as the root user.
2. Issue the following command:

/usr/local/cpanel/bin/checkallsslcerts

Documentation:

The checkallsslcerts Script

source: https://support.cpanel.net/hc/en-us/articles/360055612073-How-to-generate-a-free-hostname-certificate-with-AutoSSL