If you download the full package of this theme, unzip the package. You will see an 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 a few seconds depending upon your internet speed to upload it. After uploading the theme to will see a link to activate the theme. Click the active link to activate the theme.
Installing the theme from FTP:
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.