Downloading Hub
You can download the Hub theme ZIP package from Themeforest. Inside the ZIP package, you can find Hub.zip main theme file, Hub Core plugin and other 3rd party plugins.
Installation of Hub
Hub can be installed in two ways:
Installation via WordPress
Step 1: Navigate to Appearance > Themes.
Step 2: Click Add New and then press the Upload Theme button.
Step 3: Find the archive Hub.zip on your computer and click Install Now button.
Step 4: After the installation, the theme will appear on your WordPress dashboard, Appearance > Themes page – after installing, Hub can be activated right there.
Installation via FTP
Step 1: Connect to your hosting via an FTP client such as; Filezilla, Cyberduck
Step 2: Unzip the archive Hub.zip on your computer
Step 3: Upload the extracted theme folder into wp-content/themes in your WordPress installation
You can read more about installation via FTP following this tutorial.
For more detailed information, check out this article by Envato: https://www.envato.com/blog/install-themeforest-wordpress-theme/