To install this theme you must have a working version of WordPress already installed. For information regarding the installing of the WordPress platform, please see the WordPress Codex - https://codex.wordpress.org/Installing_WordPress.
You can install the theme just as you would install any other WordPress Theme.
To install the theme:
In the WordPress Dashboard, click on Appearance > Themes to open the Themes screen.
Click on the Add New button to open the Add Themes screen.
Click on the Upload Theme button and upload the zipped theme file you have received from ThemeForest.
Once the file is uploaded click on the Install Now button to install the theme.