Niceforms is a script that will replace the most commonly used form elements with custom designed ones. You can either use the default theme that is p
Extract the entire folder greybox-integrator into your plugins director, usually '/wp-content/plugins'
Activate the plugin on the plugin screen of WP-Admin
Use the quicktags button in your Write Post / Page window to insert the necessary code.
For detailed usage instructions please visit http://ajaydsouza.com/wordpress/plugins/greybox-integrator/using-greybox/