Your sapi-nt application can be set up and customised entirely using configuration files. These include Spring configuration files and sapi-nt specific files. Usually, these files should be written in YAML format.
The various types of configuration are documented here:
The sapi-nt archetype should provide an adequate minimal configuration for the app to run successfully, but you will need to include spec files for your data model, data source and endpoints in order to start building an API and emitting useful data.