You only need a CSR if you're installing a paid SSL certificate. The free AutoSSL certificates don't need one.
- In cPanel, open SSL/TLS in the Security section.
- Under Certificate Signing Requests (CSR), click Generate, view, or delete SSL certificate signing requests.
- Leave Key set to generate a new key (RSA 2048-bit is standard).
- Enter the domain(s), for example yourdomain.co.uk and www.yourdomain.co.uk.
- Fill in your organisation details: city, county, country (GB), company name and email.
- Click Generate.
Copy the whole CSR block, including the -----BEGIN CERTIFICATE REQUEST----- and -----END CERTIFICATE REQUEST----- lines, and give it to the certificate provider.
The matching private key is saved in cPanel automatically, ready for when you install the certificate.