docs: add "Initializing the Utility Class"

Author: kenjis

user_guide_src/source/database/utilities.rst

@@ -1,13 +1,32 @@
-#########
-Utilities
-#########
+######################
+Database Utility Class
+######################
 
 The Database Utility Class contains methods that help you manage your database.
 
 .. contents::
     :local:
     :depth: 2
 
+******************************
+Initializing the Utility Class
+******************************
+
+Load the Utility Class as follows::
+
+    $dbutil = \CodeIgniter\Database\Config::utils();
+
+You can also pass another database group to the DB Utility loader, in case
+the database you want to manage isn't the default one::
+
+    $dbutil = \CodeIgniter\Database\Config::utils('group_name')
+
+In the above example, we're passing a database group name as the first
+parameter.
+
+****************************
+Using the Database Utilities
+****************************
 
 Export a Query Result as an XML Document
 ========================================