The captive portal web server can be setup using the instructions given here. The following actions are required to use the code given in this repo:
Copy the .env.example file to the upper level folder and change its name to .env. Set the values of the given project-wide environment variables in it.
Rename the parameters.php.example file to parameters.php and set the values of variables according to the current site.
Install Composer
Then run php composer.phar install to install the packages given in composer.json.