Installation via the WordPress admin panel
After downloading the theme zip file to your local computer, please go to Appearance > Themes in your WordPress admin panel and click the Install button at the top of the page. Now click the Upload Theme button and upload the theme zip file from your computer. You can activate the theme by hovering over the preview image, here you will see the Activate button.
Installation via FTP
Alternatively you can also install the theme directly to your server with a FTP client (e.g. Filezilla). Just drop the unziped theme folder into your …/wp-content/themes/ folder. Now you can see the uploaded theme in your WordPress admin panel under Appearance > Themes > Available Themes. From there you can activate the theme.