How do I correctly configure Nginx XFF?

I am trying to follow the directions found here:

https://nginx.org/en/docs/http/ngx_http_realip_module.html

and referenced here:

https://www.loadbalancer.org/blog/nginx-and-x-forwarded-for-header/

and here:

https://stackoverflow.com/questions/43689588/how-to-set-up-realip-module-in-nginx

but I cannot seem to get it right. Here is the relevant Nginx block. Can anyone tell me where I am going wrong?

        location ^~ / {
            try_files $uri @backend;
        }

        location @backend {
            set_real_ip_from  <ip-address>;
            set_real_ip_from  <ip-address>;
            real_ip_header    X-Forwarded-For;
            
            add_header X-Frame-Options "SAMEORIGIN" always;
            add_header X-XSS-Protection "1; mode=block" always;
            add_header X-Content-Type-Options "nosniff" always;
            add_header Referrer-Policy "no-referrer-when-downgrade" always;
            add_header Content-Security-Policy "default-src * data: 'unsafe-eval' 'unsafe-inline'" always;
        }

In the first set of instructions, the author states that NGINX must be compiled with the --with-http_realip_module. But the others put the module into the config file and restart Nginx. The latter did not work for me, but that might be because I do not have the conf file configured correctly. Which is correct and if Nginx needs to be compiled with the module, can anyone point me to instructions on how to do so for Ubuntu 20.04? I have searched and cannot find additional information.

The output of nginx -V is

nginx version: nginx/1.18.0 (Ubuntu)
built with OpenSSL 1.1.1f  31 Mar 2020
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -fdebug-prefix-map=/build/nginx-KTLRnK/nginx-1.18.0=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -Wl,-z,relro -Wl,-z,now -fPIC' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --modules-path=/usr/lib/nginx/modules --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-compat --with-pcre-jit --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_v2_module --with-http_dav_module --with-http_slice_module --with-threads --with-http_addition_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module=dynamic --with-http_sub_module --with-http_xslt_module=dynamic --with-stream=dynamic --with-stream_ssl_module --with-mail=dynamic --with-mail_ssl_module