Hi,

1st, You need to apply the cert of ssl either for free or paid, and you should download the cert and put it in apache or nginx root(according to the service you are running)

for example, in apache root/cert/, if there arent any, mkdir one.

2nd, Edit the configuration file ofapache or nginx root(according to the service you are running),

for example, in apache, make sure the following works,

LoadModule ssl_module modules/mod_ssl.so

Include conf/extra/httpd-ssl.conf

3rd, Config about the support of SSL cert

4th,Config the Documentroot and Servername  about you site

 There are many documents from google, please check and hope you could figure it out.