If you download the full package of this theme, unzip the package. You will see a installable zip file there.
You can install the theme in your site by FTP or WordPress admin.
Installing the theme form WordPress dashboard:
Login to your WordPress site, navigate to Appearance > themes. Click on the Add New, then click on the Upload theme button.
Choose the Installable WordPress theme here and click install now button. Then it will take few seconds depending upon your internet speed to upload it. After uploading the theme to will see a link to active the theme. Click the active link to active the theme.
Installing the theme form FTP:
Login to your site’s FTP from any FTP client like FileZilla, Cyberduck etc. Go to the wp-content folder > themes. Unzip the installable theme file and upload it to the themes directory.
After upload complete go to your site admin and navigate to Appearance > themes. You will see this theme there. Click the active button to active the theme.