Please keep in mind that Botiga Pro is a plugin, not a theme. The theme you will be using will still be Botiga, while Botiga Pro (the plugin) will simply extend it with more options and additional demos.
First, you have to make sure that in Appearance > Themes, you have the Botiga theme installed and activated:

Once active, you can now install the Botiga Pro plugin by following these steps:
- Download the .zip package you get after purchasing the plugin;
- From your admin 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.
After successfully activating, you should be able to find the plugin in Plugins > Installed Plugins.

To activate the Botiga Pro features, go to Appearance > Theme Dashboard.
Next steps: