The installation instructions say,
Upload the folder google-plus-page-badge and its contents to the /wp-content/plugins/ directory or use the wordpress plugin installer
Activate the plugin through the ‘Plugins’ menu in WordPress
A new “Google+ Page Badge” widget will be available under Appearance > Widgets, where you can add it to your sidebar and edit all settings of the plugin.
To use the template tag or shortcodes, go to Settings > Google+ Page Badge to enter your Google+ Page ID (See FAQs for full instructions)
On my other WordPress self hosted blogs, I can do that but this is a WordPress blog.
Where do I find this to upload to if the blog is not self hosted “/wp-content/plugins/”