.htaccess – Redirect NON-www to www for https – Stack Overflow
RewriteCond %{HTTPS} !on [OR]
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule (.*) https://www.example.com%{REQUEST_URI} [L,R=301]...
Read more here: .htaccess – Redirect NON-www to www for https – Stack Overflow.