Deploy ruby on rail app to AWS(Amazon Linux) - ruby-on-rails

Question

I am following the step in https://www.sitepoint.com/deploy-your-rails-app-to-aws/ to deploy my ruby on rails app to AWS(Amazon Linux).
I did everything sucessfully except for the setting of nginx.
In the artcile, it asks me to comment out the existing content and paste the following into /etc/nginx/sites-available/default.
upstream app {
# Path to Puma SOCK file, as defined previously
server unix:/home/deploy/contactbook/shared/tmp/sockets/puma.sock fail_timeout=0;
}
server {
listen 80;
server_name localhost;
root /home/deploy/contactbook/public;
try_files $uri/index.html $uri #app;
location / {
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Host $host;
proxy_redirect off;
proxy_http_version 1.1;
proxy_set_header Connection '';
proxy_pass http://app;
}
location ~ ^/(assets|fonts|system)/|favicon.ico|robots.txt {
gzip_static on;
expires max;
add_header Cache-Control public;
}
error_page 500 502 503 504 /500.html;
client_max_body_size 4G;
keepalive_timeout 10;
}
But after I installed nginx on Amazon Linux, there is no folder /etc/nginx/sites-available
So I created this folder and file default.
But I got 404 error when I try to access my home page.
Then, I found I have /etc/nginx/nginx.conf, so I updated this file. But when I did sudo service nginx restart, I got error msg as:
nginx: [emerg] "upstream" directive is not allowed here in /etc/nginx/nginx.conf:1
nginx: configuration file /etc/nginx/nginx.conf test failed
Does anyone know how should I do this correctly?
FYI, the content of /etc/nginx/nginx.conf before I broke it:
# For more information on configuration, see:
# * Official English Documentation: http://nginx.org/en/docs/
# * Official Russian Documentation: http://nginx.org/ru/docs/
user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
log_format main '$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 2048;
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;
index index.html index.htm;
server {
listen 80 default_server;
listen [::]:80 default_server;
server_name localhost;
root /usr/share/nginx/html;
# Load configuration files for the default server block.
include /etc/nginx/default.d/*.conf;
location / {
}
# redirect server error pages to the static page /40x.html
#
error_page 404 /404.html;
location = /40x.html {
}
# redirect server error pages to the static page /50x.html
#
error_page 500 502 503 504 /50x.html;
location = /50x.html {
}
# proxy the PHP scripts to Apache listening on 127.0.0.1:80
#
#location ~ \.php$ {
# proxy_pass http://127.0.0.1;
#}
# pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
#
#location ~ \.php$ {
# root html;
# fastcgi_pass 127.0.0.1:9000;
# fastcgi_index index.php;
# fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name;
# include fastcgi_params;
#}
# deny access to .htaccess files, if Apache's document root
# concurs with nginx's one
#
#location ~ /\.ht {
# deny all;
#}
}
# Settings for a TLS enabled server.
#
# server {
listen 443 ssl;
# listen [::]:443 ssl;
# server_name localhost;
# root /usr/share/nginx/html;
#
# ssl_certificate "/etc/pki/nginx/server.crt";
# ssl_certificate_key "/etc/pki/nginx/private/server.key";
# # It is *strongly* recommended to generate unique DH parameters
# # Generate them with: openssl dhparam -out /etc/pki/nginx/dhparams.pem 2048
# #ssl_dhparam "/etc/pki/nginx/dhparams.pem";
# ssl_session_cache shared:SSL:1m;
# ssl_session_timeout 10m;
# ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
# ssl_ciphers HIGH:SEED:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK:!RSAPSK:!aDH:!aECDH:$
# ssl_prefer_server_ciphers on;
#
# # Load configuration files for the default server block.
# include /etc/nginx/default.d/*.conf;
#
# location / {
# }
error_page 404 /404.html;
# location = /40x.html {
# }
#
# error_page 500 502 503 504 /50x.html;
# location = /50x.html {
# }
# }
}