Login into your admin section in WordPress (http://your-site.com/wp-admin)
Go to Appearance - Themes.
Click Add New and hit the Upload button.
Browse to find "landkit.zip" (you can find the zip in the extracted package folder) file on your computer and click Install Now.
The theme will be uploaded and installed.
Activate the installed theme.
Our themes use Hybrid Composer plugin to run so make sure you install and activate it. Go to Plugins and Install / Activate Hybrid Composer. Don't worry, it's a plugin developed by us and it's completely integrated with the theme.