Extract the zipped package downloaded from ThemeForest to your desktop. In the extracted package you will find the doxy.zip file which is an installable WordPress theme.
You can install the theme in two different ways:
1. WordPress theme uploader
Navigate to Appearance -> Themes to access the theme uploader screen and use the doxy.zip file.
Extract the doxy.zip file and upload the extracted doxy folder to
/wp-content/themes/ the folder on your server. You will have to use FTP software, like FileZilla.
After uploading the theme, you have to activate it. Navigate to Appearance -> Themes page to activate the theme.