We are still working on supporting intranet sites properly:
Because the site is not accessible from the public, you first have to add a random site to your account that exists on the public internet. After that, click on the site in the dashboard and scroll to the bottom until you see “Manage Website”. In this section, change the URL to the URL of your intranet site and change CMS to WordPress in case the site runs on WordPress and you would like to install the firewall on the intranet site.
After that, refresh the page and click on “Setup Plugin” > “I want to install the plugin manually” on the bottom and then go through the steps to install the plugin manually.
Note that uptime monitoring will not work on intranet sites.