Multisite – add www on site URL

Hi guys, I need some help.

I have a wordpress site installed on https://www.domain.com/info/wp that was already installed by someone else.
However, instead of accessing the site on https://www.domain.com/info/wp, the site URL will be pointed to https://www.domain.com/info/. To do this, there were 2 htaccess files – one is located on /info and the other one is on /wp.

There’s also an index.php file under /info that contains these codes:

<?php
/**
 * Front to the WordPress application. This file doesn't do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 */
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require('./wp/wp-blog-header.php');
?>

I tried to set up a Multisite after with these settings and added some lines on the config.php file and the two htaccess files. Everything works fine except that the site that I created under multisite looks like this:
https://domain.com/info/site2

and I want to change it to:
https://www.domain.com/info/site2

I know it’s possible to do it via htaccess but I don’t know how.

Additional info
Here’s what the htaccess on /info folder looks like:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /info/
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) wp/$2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ wp/$2 [L]
RewriteRule . /info/index.php [L]
</IfModule>

# END WordPress

And the htaccess of /info/wp:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /info/wp/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /info/wp/index.php [L]
</IfModule>

# END WordPress

Any help will be much appreciated.