The API CSS is in the file
You can customize your API by editing the file
see: API constants definition <https://camptocamp.github.io/ngeo/master/jsdoc/module-api_src_options.html>
The API help is in the folder
In order for a layer to be accessible via API, proceed as follows:
Add the layer.
Select the ‘api’ interface.
Add the layer to a group which is visible in the API.
A group is visible in the API if it is in a theme whose ‘api’ interface is checked.