$ sudo apt-get update
$ sudo apt-get install itcl3-doc 

itcl3-doc is installed in your system.

Make ensure the itcl3-doc package were installed using the commands given below,

$ sudo dpkg-query -l | grep itcl3-doc *

You will get with itcl3-doc package name, version, architecture and description in a table

itcl3-doc package basic information: