Run these commands
1. openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/nginx/ssl/example.key -out /etc/nginx/ssl/example.crt
2.mkdir /etc/nginx/ssl
3.chmod 777 /etc/nginx/ssl
4.vi /etc/nginx/conf.d/default.conf
listen       80 ssl;
   server_name  localhost;
   ssl_certificate /etc/nginx/ssl/example.crt;
   ssl_certificate_key /etc/nginx/ssl/example.key;

5. nginx -t
6. nginx -s reload