Thanks for using Bitnami. For the email you need to specify a valid email address that Let's Encrypt can use to associate it with the domain name and contact you in case it is necessary (e.g. to inform you that the SSL certificate is about to expire).
For the domain name, you need to configure a DNS provider to link your desired domain name to your server IP address so you can access to your server using a domain name instead of an IP address.
Once you have configured a domain name pointing to your server IP address, you will need to configure Mautic for using that domain name internally. You can find more information about how to configure it in the guide below
Then, you can use the
generate-certificate.sh script and provide the domain name that you selected in your DNS provider for the domain arguments.
Let us know any other question you may have.