The following code will help you in redirecting your website to https://www.domainname.com. Also, it will solve the canonical domain name issue.
Copy the following code to your .htaccess file lying in the root directory. If not, create it and paste the below code:
RewriteCond %{HTTPS} off
# First rewrite to HTTPS:
# Don't put www. here. If it is already there it will be included, if not
# the subsequent rule will catch it.
RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
# Now, rewrite any request to the wrong domain to use www.
# [NC] is a case-insensitive match
RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteRule .* https://www.%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
RewriteEngine On
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.php
RewriteRule ^index\.php$ / [L,R=301]
Options -Indexes
