Extract the zipped package downloaded from ThemeForest to your desktop and find hubble-theme.zip file. You can install the theme using admin panel or FTP.
Go to WordPress admin panel -> appearance -> themes and then Add new -> upload theme and upload the theme zip file. After installation, you must activate the theme as well.
For any reason if you failed to upload theme with WordPress admin panel, you can also do it using FTP. Unzip the theme zip file and upload hubble folder to WordPress root -> wp-content -> themes then go to admin panel -> appearance -> themes and activate the Eram theme.
After that you need to install and activate hubble theme plugin.
When you activate the theme you will be redirected to a welcome screen. There you can install required plugins.