Enable HTTPS via WordPress Settings -
1. Login to your WordPress admin page, click on Settings and General.
2. You now need to update your WordPress Address (URL) and Site Address (URL) from http:// to https://
3. Press Save at the bottom
Enable HTTPS via .htaccess code -
1. Go to File Manager in cPanel and go to your public_html folder (or the folder of the addon domain you're enabling this on).
2. Click Settings in the top right and toggle the option "Show Hidden Files (dotfiles)" and press Save.
3. Click the file called .htaccess and press "Edit" at the top of the file manager.
4. Add the following code below what's currently there:
#Force SSL on Entire Site RewriteEngine On RewriteCond %{HTTPS} off RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}