Extract the zipped package downloaded from ThemeForest to your desktop, in the extracted package you will find the safarica.zip file which is the WordPress theme.
You can install the theme in two different ways:
Extract the safarica.zip file and upload the extracted folder to /wp-content/themes/ folder on your server. You will have to use some FTP software, like FileZilla.
Navigate to Appearance -> Add New Themes -> Upload page. Select safarica.zip file. Press the Install Now button to upload and install the theme.
After uploading the theme, you have to activate it. Navigate to Appearance -> Themes page to activate the theme.
Check this page made by ThemeForest on how to install a WordPress theme correctly: ThemeForest knowledge base
Watch the complete process in this short video: