Extensions can be quite useful and save a lot of hacker time when well used. In order to install and enable an extension do the following;

1. Upload the extension into your extensions folder inside your EE system folder.
2. If there is a language file that accompanies the extension, upload that into the appropriate sub=folder of your language folder.
3. Go to Utilities > Extension Manager
4. In the extensions manager, ensure that the extensions capability is enabled for your site.
5. In the extensions manager, enable the extension that you uploaded.
6. If there are settings for the extension you enabled, set those.
7. Follow the instructions in the extension documentation. In most cases you will be adding parameters to existing EE tags within your templates.