Please keep in mind that Wpazure Pro is a plugin, not a theme. The theme you will be using will still be Wpazure, while Wpazure Pro (the plugin) will simply extend it with more options.
To install Wpazure Pro, please follow these steps:
Download the .zip package you get after purchasing the Wpazure pro;
From your Member area, navigate to Plugins > Add New;
Locate the Upload Plugin button at the top-left side of the page and click on it;
Click on Choose file and locate the .zip package you’ve downloaded, then click on Install Now;
Activate the plugin and you’re done.