Hi
The file you have download is the theme package zip file where include tatoo-pro.zip, xml file, sql file, installation guide and theme documentation so when you finish the download just extract (unzip) the theme package on your desktop or laptop and then you just need to upload tatoo-pro.zip file in the WordPress.
If you still facing the issue then kindly send us the site URL and the login details so we can install and setup the theme.
Thank You