Q : What are the things I have to prepare/do to install SSL or enable https:// on my domain.
1) You need dedicated IP for your domain. e.g. 18.104.22.168 which is dedicated for your domain only. No other domain should associate with it (not shared IP). You can usually subscribe for dedicated IP service from your share hosting company for $2/month. Some hosting like IXwebhosting gives free dedicated IP.
2) Decide which SSL domain – e.g. https://www.yourdomain.com is different from https://yourdomain.com . The choice is yours, it depends on which one you like it more.
3) Prepare A CSR. A certificate signing request or CSR is a piece of text that must be generated on your web server before ordering the SSL certificate. The certificate authority will use the information contained in the CSR (Organization name, domain name, public key, etc…) to create your certificate. Your host will be able to help you.
4) Submit the CSR and other info to the Certificate Authority (aka your SSL service provider).
5) Certificate Authority will return a signed certificate and ready for installation.