Dejar mi web unicamente con acceso via www  

Hola

Creo que Google ya te contempla este punto cuando configuras Dominio preferido desde Search Console.
Sin embargo si quieres hacer la redirección efectivamente tienes que usar el código que se indica en el artículo, no he podido revisar tu .htaccess por alguna razón no lo puedo descomprimir, asegúrate de que la redirección sea el primero código de tu archivo.

Saludos.

Hola Jhon, pondre aqui el codigo del .htaccess para analizarlo y me indiques por favor donde poner las lineas de codigo necesario para lo que necesito:

SetHandler application/x-lsphp70

Header set Expires "Wed, 15 Apr 2020 20:00:00 GMT"
Header set Cache-Control "public"

SetOutputFilter DEFLATE

##
# @package Joomla
# @copyright Copyright (C) 2005 - 2015 Open Source Matters. All rights reserved.
# @license GNU General Public License version 2 or later; see LICENSE.txt
##

##
# READ THIS COMPLETELY IF YOU CHOOSE TO USE THIS FILE!
#
# The line just below this section: 'Options +FollowSymLinks' may cause problems
# with some server configurations. It is required for use of mod_rewrite, but may already
# be set by your server administrator in a way that disallows changing it in
# your .htaccess file. If using it causes your server to error out, comment it out (add # to
# beginning of line), reload your site in your browser and test your sef url's. If they work,
# it has been set by your server administrator and you do not need it set here.
##

## No directory listings
IndexIgnore *

## Can be commented out if causes errors, see notes above.
Options +FollowSymlinks
Options -Indexes

## Mod_rewrite in use.

RewriteEngine On

## Begin - Rewrite rules to block out some common exploits.
# If you experience problems on your site block out the operations listed below
# This attempts to block the most common type of exploit `attempts` to Joomla!
#
# Block out any script trying to base64_encode data within the URL.
RewriteCond %{QUERY_STRING} base64_encode[^(]*([^)]*) [OR]
# Block out any script that includes a tag in URL.
RewriteCond %{QUERY_STRING} (|%3E) [NC,OR]
# Block out any script trying to set a PHP GLOBALS variable via URL.
RewriteCond %{QUERY_STRING} GLOBALS(=|[|%[0-9A-Z]{0,2}) [OR]
# Block out any script trying to modify a _REQUEST variable via URL.
RewriteCond %{QUERY_STRING} _REQUEST(=|[|%[0-9A-Z]{0,2})
# Return 403 Forbidden header and show the content of the root homepage
RewriteRule .* index.php [F]
#
## End - Rewrite rules to block out some common exploits.

## Begin - Custom redirects
#
# If you need to redirect some pages, or set a canonical non-www to
# www redirect (or vice versa), place that code here. Ensure those
# redirects use the correct RewriteRule syntax and the [R=301,L] flags.
#
## End - Custom redirects

##
# Uncomment following line if your webserver's URL
# is not directly related to physical file paths.
# Update Your Joomla! Directory (just / for root).
##

# RewriteBase /

## Begin - Joomla! core SEF Section.
#
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
#
# If the requested path and file is not /index.php and the request
# has not already been internally rewritten to the index.php script
RewriteCond %{REQUEST_URI} !^/index.php
# and the requested path and file doesn't directly match a physical file
RewriteCond %{REQUEST_FILENAME} !-f
# and the requested path and file doesn't directly match a physical folder
RewriteCond %{REQUEST_FILENAME} !-d
# internally rewrite the request to the index.php script
RewriteRule .* index.php [L]
#
## End - Joomla! core SEF Section.

Hola

Puedes ponerlo al inicio de todo, antes de lo que envías en tu mensaje anterior.

No olvidar reemplazar "misitioweb" por el dominio de tu sitio
https://www.webempresa.com/blog/como-mejorar-el-seo-de-tu-web-con-joomla-3.html

Saludos.

Entiendo Jhon, gracias por la orientación.