$ sudo apt-get update
$ sudo apt-get install modsecurity-crs 

modsecurity-crs is installed in your system.

Make ensure the modsecurity-crs package were installed using the commands given below,

$ sudo dpkg-query -l | grep modsecurity-crs *

You will get with modsecurity-crs package name, version, architecture and description in a table

modsecurity-crs package basic information: