From Classyfrieds version :  2.4

The classyfrieds ads and notices expansion plugin provides you, the administrator, with several new options to include advertisements or notices in your classifieds and listings system. This classyfrieds extension installs just like a regular WordPress plugin, and only shows itself in the classyfrieds section of your blog.

Once installed and activated the plugin will create a new submenu page in your classyfrieds admin user interface.

In your administration panel you can enter or paste any html , javascript or regular text, and have it displayed automatically above your listings in the main index. You can also include news right above and/or right below the main content in the listings.

Increase your earnings by simply pasting a few google adsense codes, or include entire html forms. Provide notices and generic disclaimers to your visitors and so much more …. The options are limitless as you can even provide your own CSS layout inside the boxes and generate truly unique content.

install instructions :
ALL classyfrieds extensions install like regular WordPress plugins.
So to install classyfrieds plugins simply go to your wordpress administation panel -> plugins -> add new -> then use the upload button to install the downloaded .zip file from your computer. Once upload is complete simply activate the plugin and new menu options will appear in the classyfrieds main menu.