You can easily have the booking form placed on multiple pages within the same domain. Open each of the pages in Pages > All Pages > Edit and click on the "Add Bookly booking form" button. All activity from all pages will be stored in one admin area.
In order to use the plugin on several domains, you'll need to get the Bookly Multisite Add-on. As per confirmation by Envato the CodeCanyon team (the platform where Bookly is being distributed), you'll then have to purchase a separate Bookly license for each domain and then enter each of the purchase codes to link them to the Multisite add-on.