install ssl certificate on self hosted linux server

I need help to install an SSL certificate on a self-hosted Linux server. I have root access to the server and it is running Turnkey GNU/Linux with Apache. I'm not sure what type of SSL certificate I need to install, so I need guidance on which one to get. Every website needs a secure connection, which is why I am seeking help to install an SSL certificate to my self-hosted Linux server. The right person can help me to make sure my site is secure and protected from any malicious threats.