Porto is Static HTML5/CSS3/JS Template, there is no Admin Panel/Dashboard to Drag/Drop the Elements on the Pages (and no installation process). You will need to manually Edit the Codes to add your Content using Sublime Text or an Equivalent Text/Code Editor.
When you finish editing your website, You will need to upload these files to your web server using FTP.
Note that it works the same way for all HTML templates on ThemeForest.
All the files that come with the zip package you downloaded can be used as a base/start for your project, the main idea is that you don’t have to start from scratch, just use an existing page from the demo and modify according to your needs (choosing a HTML file that is more similar to the page you want to build).
Regarding the Bootstrap 4:
Don’t is necessary install the BS4 on Cpanel first. Porto already comes with BS4.