In order to have a secure website it’s not enough to use a certificate, you need to configure the server to use the right cryptography and hashing algorithms.
1. For IIS Web Servers the following tool will help configure the corect cipher suites you want to use.
2. For other Web Servers (Apache, Nginx) use the following link to configure the server:
3. Also make sure to enable HTTP Strict Transport Security.
You can also verify the security of your website here: https://www.ssllabs.com/ssltest/