Firstly you need to make sure that you have a working SSL certificate installed n your account.
You can redirect users by adding the following lines of code to your .htaccess file located in: /public_html/
RewriteEngine on #Options +FollowSymlinks RewriteCond %{SERVER_PORT} ^80$ RewriteRule ^(.*) https://yourdomain.com/cart/$1 [R,L]