IFRAME Embed For YouTube will add a quicktag on WordPress Post Editor which will add the capability to embed Youtube Videos thru IFRAME, just you need
This plugin is easy to install like other plug-ins of WordPress as you need to just follow the below mentioned steps:
Copy Folder 'iframe-embed-for-youtube' from the downloaded and extracted file.
Paste it in 'wp-Content/plugins' folder on your WordPress Installation
Activate the plugin from Dashboard / Plugins window.
Now Plugin is Activated, Go to the Usage section to see how to use Iframe Embed For YouTube.