This is a Firefox extension that allows you to set CogiSearch as a search engine for Firefox, or even as the default one.
This has been created because Firefox removed the ability to add custom search engines easily.
You can find it here: https://addons.mozilla.org/en-US/firefox/addon/cogisearch/
If you want to install it manually, you can download the latest version from the releases page. However, it is recommended to use the Firefox addon.
This is just the extension, if you want to know more about CogiSearch, you can find more infos on Cogilabs.eu, or even on CogiSearch itself.