Add stub on how to launch plasma and add to toctree.

source/4/4.1/discover.rst

@@ -0,0 +1,11 @@
+Chapter 4.1 Discover
+====================
+Discover is a software center that can graphically manage packages to install different programs and utilities.
+
+Version
+-------
+Lubuntu ships with version 5.13.5 of discover. 
+
+How to launch
+-------------
+To luanch Discover from the menu -> System Tools -> Discover or run plasma-discover from the command line. 

source/4/Installing_Updating_and_Removing_Software.rst

@@ -5,3 +5,4 @@ Chapter 4 Installing_Updating_and_Removing_Software
   :maxdepth: 2
   :titlesonly:
 
+  4.1/discover