$ sudo apt-get update
$ sudo apt-get install gosa-help-nl 

gosa-help-nl is installed in your system.

Make ensure the gosa-help-nl package were installed using the commands given below,

$ sudo dpkg-query -l | grep gosa-help-nl *

You will get with gosa-help-nl package name, version, architecture and description in a table

gosa-help-nl package basic information: