If you don’t already have wordpress installed, please follow instructions for installation which can be found here.
The easiest and quickest way to install the theme is to simply upload zip file from Appearance > Themes menu in wordpress. Click on Add new button and than Upload theme. Here you can select .zip file which you downloaded on your computer and it will be installed automatically. Now it’s just left to click on Activate button to activate the theme.
Another way to install the theme is using FTP. In case you get error message like max upload size exceeded than you will need to upload files manually. Unzip downloaded theme file on your computer and move entire folder to wp-content/themes directory on server where wordpress is installed. When you have this folder uploaded, visit Appearance > Themes section in wordpress admin and new theme should be visible in this area for activation.
Installation also can be done using your hosting file manager or cPanel. In this case you don’t have to unzip the file if your hosting supports zip/unzip option in control panel. Upload .zip file in the same wp-content/themes directory and unzip it on server. Last step is to go to Appearance > Theme menu again and activate the theme.