Per the Django Tutorials Polls App:

to include the app in our project, we need to add a reference to its configuration class in the INSTALLED_APPS setting. ThePollsConfig class is in the polls/ file, so its dotted path is 'polls.apps.PollsConfig'. Edit the mysite/ file and add that dotted path to the INSTALLED_APPS setting. It’ll look like this:

what is the syntax for setting something up in the installed_appps setting.

is it the app name.apps keyword than . AppNameConfig?

How does that work?

The syntax is exactly as shown in the tutorial.

This is all using standard Python syntax. See 5. The import system — Python 3.11.4 documentation if you want more details.