Buy the cheapest one
Paid by paypal, then
Step 1.
on comodo, need Input CSR (Certificate Signing Request)
1.1 cpanel > SSL / TLS > click SSL certificate signing request
1.2 cpanel > SSL / TLS > click SSL certificate signing request
1.3 fill out: Generate a New Certificate Signing Request (CSR)
1.4 copy CSR
-----BEGIN CERTIFICATE REQUEST-----
-----END CERTIFICATE REQUEST-----
1.4 copy private key
-----BEGIN RSA PRIVATE KEY-----
-----END RSA PRIVATE KEY-----
1.5 paste on comodo page, then continue
Step 2. domain verification
2.1
2.2
2.3