Based on the issue you noted, and given that you selected a domain name that is publicly resolvable (passbolt.net), you might want to change the hostname to a domain that you own.
Or, if you are attempting to use passbolt.net for internal use only, you will need to establish a route to your server from your web browser’s machine. If you are trying to access via a laptop, for example, the “hosts” file for your laptop might need to be modified so that it knows which IP to request passbolt.net from. (Or, like the instructions will prompt, just use your IP address for the hostname.)