Ha, you caught me out. I didn't know how to do it when I wrote those docs :)
However, I've just done the following on Ubuntu and it worked, so I suggest this. I'm not sure it's the best way but it's the only way I can find to make it work when you have another site being the default. I'm no expert on configuring nginx.
All I did was to copy the following into my existing default config, inside the server section. On Ubuntu this is the file /etc/nginx/sites-available/default. Remember to set the fastcgi_pass parameter as appropriate to the version numbers on your system.
location /rompr/ {
allow all;
index index.php;
location ~ \.php {
try_files $uri index.php =404;
fastcgi_pass unix:/var/run/php/php7.1-fpm.sock;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME $request_filename;
include /etc/nginx/fastcgi_params;
fastcgi_read_timeout 1800;
}
error_page 404 = /404.php;
try_files $uri $uri/ =404;
location ~ /albumart/* {
expires -1s;
}
}
Now you ned to symlink your rompr installation into the default directory structure. The directory I'm going to refer to as /ROOT/DIRECTORY here is the one specified as 'root' in your existing default config file
sudo ln -s /PATH/TO/ROMPR /ROOT/DIRECTORY/rompr
where /PATH/TO/ROMPR is as referred to in the docs.
Then restart nginx and you should have a http://your.host/rompr working.