This is to recap the steps outlined in this digital ocean’s post

Setup Firewall

sudo firewall-cmd --add-port=443/tcp --permanent
sudo firewall-cmd --add-port=80/tcp --permanent
sudo firewall-cmd --reload

Install Nginx

sudo yum install nginx

Configure Nginx for Domain Validation

Let’s Encrypt needs to know that you are the legitimate domain owner. The easiest way to prove this is to add a path in nginx that Let’s Encrypt public server can call and validate

$ sudo vi /etc/nginx/default.d/le-well-known.conf

location ~ /.well-known {
  allow all;
}

$ sudo systemctl restart nginx

Obtain the cert

$ sudo certbot certonly -a webroot --webroot-path=/usr/share/nginx/html -d example.com -d www.example.com

Generate Strong Diffie-Hellman Group

$ sudo openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048

Add Cert to Nginx

## /etc/nginx/conf.d/ssl.conf

server {
  listen 443 http2 ssl;
  server_name example.com www.example.com;
  ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;

  #################################################################
  # from https://cipherli.st/ 
  #and https://raymii.org/s/tutorials/Strong_SSL_Security_On_nginx.html         ###########################################################

  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
  ssl_prefer_server_ciphers on;
  ssl_ciphers “EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH”;
  ssl_ecdh_curve secp384r1;
  ssl_session_cache shared:SSL:10m;
  ssl_session_tickets off;
  ssl_stapling on;
  ssl_stapling_verify on;

  resolver 8.8.8.8 8.8.4.4 valid=300s;
  resolver_timeout 5s;

  # Disable preloading HSTS for now. You can use the commented out header line that includes
  # the “preload” directive if you understand the implications.

  add_header Strict-Transport-Security “max-age=63072000;includeSubdomains; preload”;
  add_header Strict-Transport-Security “max-age=63072000;includeSubdomains”;
  add_header X-Frame-Options DENY;
  add_header X-Content-Type-Options nosniff;

##################################

# END https://cipherli.st/ BLOCK #

##################################

  ssl_dhparam /etc/ssl/certs/dhparam.pem;

  location ~ /.well-known {
    allow all;
  }

  # The rest of your server block
  root /usr/share/nginx/html;
  index index.html index.htm;

  location / {
    # First attempt to serve request as file, then
    # as directory, then fall back to displaying a 404.
    try_files $uri $uri/ =404;
  }
}

Setup HTTP redirects to HTTPs

$ sudo vi /etc/nginx/default.d/ssl-redirect.conf

return 301 https://$host$request_uri;

$ sudo systemctl restart nginx

Enable Nginx

$ sudo systemctl enable nginx

Setup Auto Renewal

$ sudo certbot renew
$ sudo crontab -e

30 2 * * 1 /usr/bin/certbot renew >> /var/log/le-renew.log
35 2 * * 1 /usr/bin/systemctl reload nginx

$ sudo systemctl restart nginx