nginxにおける、CORS設定

前提・実現したいこと

超初心者です。
現在webサイトを作成していて、
あるサイトから自身のサーバー(nginx)内にあるファイルにアクセスしたいです。
どうすればこのエラーを回避して、ファイルにアクセスできるでしょうか。

発生している問題・エラーメッセージ

アクセスすることができず、以下のメッセージが表示されます。

Failed to load resource: the server responded with a status of 403 ()
Access to image at 'xxxxxxxxx.com/html/good_red.png' from origin 'https://my.matterport.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

調べたこと

https://qiita.com/rysk92/items/e5cf2fab8531f8ea3683
や
https://qiita.com/tukiyo3/items/8124d5066737debdc6bb
を読みましたが、その構文をnginx.configのどこに入れればいいかわからないです。

ソースコード

nginx.configです

# For more information on configuration, see:
#   * Official English Documentation: http://nginx.org/en/docs/
#   * Official Russian Documentation: http://nginx.org/ru/docs/

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

# Load dynamic modules. See /usr/share/doc/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;

events {
    worker_connections 1024;
}

http {
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile            on;
    tcp_nopush          on;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 4096;

    include             /etc/nginx/mime.types;
    default_type        application/octet-stream;

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;

    server {
        listen       80;
        listen       [::]:80;
        server_name  _;
        root         /usr/share/nginx/html;

           location / {
       add_header Access-Control-Allow-Origin *;
       add_header Access-Control-Allow-Methods "POST, GET, OPTIONS";
       add_header Access-Control-Allow-Headers "Origin, Authorization, Accept";
       add_header Access-Control-Allow-Credentials true;
       proxy_pass http://localhost:8888;
    }

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        error_page 404 /404.html;
            location = /40x.html {
        }

        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }
    }

# Settings for a TLS enabled server.
#
#    server {
#        listen       443 ssl http2;
#        listen       [::]:443 ssl http2;
#        server_name  _;
#        root         /usr/share/nginx/html;
#
#        ssl_certificate "/etc/pki/nginx/server.crt";
#        ssl_certificate_key "/etc/pki/nginx/private/server.key";
#        ssl_session_cache shared:SSL:1m;
#        ssl_session_timeout  10m;
#        ssl_ciphers PROFILE=SYSTEM;
#        ssl_prefer_server_ciphers on;
#
#        # Load configuration files for the default server block.
#        include /etc/nginx/default.d/*.conf;
#
#        error_page 404 /404.html;
#            location = /40x.html {
#        }
#
#        error_page 500 502 503 504 /50x.html;
#            location = /50x.html {
#        }
#    }

}

javascriptコード

  var iframe;
  var tags;
  var tagg;
  var count;
  count = 0;



  document.addEventListener('DOMContentLoaded', () => {
    iframe = document.getElementById('showcase_iframe');
    iframe.addEventListener('load', showcaseLoader, true);
  });



  function showcaseLoader() {
    authorize();
    try {
      window.MP_SDK.connect(iframe, 'f2f3b17ffcdb4e99afbcc0c285a9d7c7', '3.5')
        .then(loadedShowcaseHandler) 
        .catch(handleError);
    }
    catch (e) {
      console.error(e);
    }
  }


  function loadedShowcaseHandler(mpSdk) {
    var popup = document.getElementById('js-popup');
    var mattertagDesc = {
      label: 'Hello Mattertag',
      description: 'This is test',
      anchorPosition: { x: 0.39, y: 1.00, z: -0.122 },
      stemVector: { x: 0, y: 0, z: 0 },
      color: { r: 0.0, g: 0.0, b: 1.0 },
    };
    mpSdk.Mattertag.add(mattertagDesc).then(function (mattertagId) {
      console.log(mattertagId);
      // output: TODO
    });

//ここでエラーを吐いてしまいます
    mpSdk.Mattertag.registerIcon('GoodBlackIconId', 'good_black.png');
    mpSdk.Mattertag.registerIcon('GoodRedIconId', 'http://ec2-18-224-7-206.us-east-2.compute.amazonaws.com/html/good_red.png');

    tags = mpSdk.Mattertag.getData()
    .then(function (tags){
        console.log(tags);
        tag0 = tags[0].sid;
        tag1 = tags[1].sid;
        tag2 = tags[2].sid;





      });