Hi Rose,
Thank you for writing in, while that is outside the scope of support, I could point you in the right direction with the understanding that it would ultimately be your responsibility to take it from here. First, please setup a Child theme because you’re going to need to this later.
then install the ACF Pro extension this extension allows you to create custom fields for any post type.
Then log in to your server via FTP or cPanel’s File Manager and navigate to this directory \wp-content\themes\pro\framework\views\{stack name}
the stack name is the name of the stack you use (e.g. integrity, renew, icon, ethos), in that directory look for the file content-portfolio.php
and copy that to your child theme \pro-child\framework\views\{stack name}
directory, create the directory if it does not exist.
Then edit that file to output your custom fields (title and subtitle).
Integrated Plugins - ACF Pro
Hope it helps,
Cheers!