installing packages in Guix System

[Gottfried]

I started to read the manual, but didn´t yet come across this.

When you install a package in an other Linux distro, it will be 
available in the system.

In guix it is different. I installed e.g. hplip, 
system-config-printer,cups, cups-filters, but additionally I have to add 
the printer settings in the /etc/config.scm file.

Could somebody explain it to me why?

When I installed printer packages, where do they go? Is the guix system 
on a different level and it needs also to be configured additionally?

Gottfried