There are several ways to set up a redirect from http to https protocol.
The easiest way is to enable redirection in the Directadmin web hosting control panel.
To do this, enter the control panel hosting Directadmin, go to “Setting domains
Select from the list your domain for which you wish to set up redirects.
Then make sure that the “Secure SSL” checkbox is checked. From the drop-down list select where to redirect to and check “Forced SSL https redirect” as shown on the screenshot below.
Also redirect can be set up manually by making entries in your .htaccess file. If you do not have such a file, then create it in the root of the site.
And put that code in there.
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^(.*)$ https://%{HTTP_HOST}/$1 [R=301,L]